Vehicle illumination lamp

ABSTRACT

A vehicle headlight ( 1 ), which is one aspect of a vehicle illumination lamp, includes: light sources ( 52 R,  52 G,  52 B), and diffraction gratings ( 54 R,  54 G,  54 B) for diffracting light incident from the light sources ( 52 R,  52 G,  52 B). The light diffracted by the diffraction gratings ( 54 R,  54 G,  54 B) is irradiated in a predetermined light distribution pattern. A projection area (AR) to which are projected components (LC R , LC G , LC B ) advancing and passing through the diffraction gratings ( 54 R,  54 G,  54 B) among the light incident on the diffraction gratings ( 54 R,  54 G,  54 B) is positioned below the light distribution pattern and within a range (RNG) in which a field of view of a driver of a vehicle is obstructed by the vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 16/608,357, filed Oct. 25, 2019, which is a National Stage ofInternational Application No. PCT/JP2018/015112 filed Apr. 10, 2018,claiming priority based on Japanese Patent Application No. 2017-090706filed Apr. 28, 2017, Japanese Patent Application No. 2017-090707 filedApr. 28, 2017, Japanese Patent Application No. 2017-090708 filed Apr.28, 2017, Japanese Patent Application No. 2017-090709 filed Apr. 28,2017 and Japanese Patent Application No. 2017-0907010 filed Apr. 28,2017.

TECHNICAL FIELD

The present invention relates to a vehicle illumination lamp and avehicle headlight.

BACKGROUND ART

A vehicle headlight represented by an automobile headlight is configuredto at least irradiate a low beam for illuminating the front at night. Inorder to form a light distribution pattern of this low beam, a shade isused for shielding a part of light emitted from a light source. However,due to the diversification of vehicle designs, there is a demand forreducing the size with respect to a vehicle headlight.

Patent Literature 1 describes a vehicle headlight that can form a lightdistribution pattern of a low beam without using a shade. This vehicleheadlight includes a hologram element, and a light source thatirradiates the hologram element with reference light. The hologramelement is calculated so that diffracted light reproduced by irradiatingthe reference light forms a light distribution pattern of a low beam.Since this vehicle headlight forms a light distribution pattern of a lowbeam by such a hologram element, a shade is not required, and areduction in size is possible.

-   [Patent Literature 1] JP2012-146621 A

SUMMARY OF INVENTION

A vehicle illumination lamp of the present invention includes a lightsource, and a diffraction grating for diffracting light incident fromthe light source, in which light diffracted by the diffraction gratingis irradiated in a predetermined light distribution pattern, and aprojection area to which are projected components advancing and passingthrough the diffraction grating among the light incident on thediffraction grating is positioned below the light distribution patternand within a range in which a field of view of a driver of a vehicle isobstructed by the vehicle.

The components advancing and passing through the diffraction gratingcorrespond to 0th-order light, and have a high light intensity comparedto a light intensity of high order light from 1st-order light onwards.However, in the vehicle illumination lamp according to the presentinvention, since the projection area to which are projected thecomponents corresponding 0th-order light is positioned within a rangewhere a field of view of a driver of a vehicle is obstructed by thevehicle, it is possible to suppress a reduction in a driver's ability topay attention due to the components. Accordingly, it can be easier tooperate compared to the case where 0th-order light is in a field of viewof a driver of an automobile.

Moreover, the light distribution pattern may be a light distributionpattern of a low beam. In this case, in the vehicle illumination lamp ofthe present invention, a light distribution pattern of a low beam can beformed without using a shade, by having light diffracted by thediffraction grating irradiated in a light distribution pattern of thelow beam. Accordingly, it is possible to reduce in size compared to avehicle illumination lamp that uses a shade.

Moreover, the light distribution pattern may have a light intensitydistribution. In this case, if a light intensity distribution is set inwhich a central portion of the light distribution pattern is bright andperipheral portions other than the central portion are relatively dark,it is possible to achieve a natural light distribution pattern that doesnot provide a driver with a sense of discomfort.

Moreover, it may include a plurality of light emitting optical systemsincluding one light source and one diffraction grating, and a synthesisoptical system for synthesizing light emitted from the respective lightemitting optical systems, the light sources in the respective lightemitting optical systems may emit light of mutually differentpredetermined wavelengths, and the diffraction gratings in therespective light emitting optical systems may diffract light from thelight sources so that the light synthesized by the synthesis opticalsystem has a light distribution pattern of a low beam.

In this case, in the respective light emitting optical systems, light ofa predetermined wavelength emitted from the light source is diffractedby the diffraction grating, and a light distribution pattern is formed.At this time, in the respective light emitting optical systems, sincelight diffracted by the diffraction grating has a predeterminedwavelength such as described above, it is possible to suppress colorbleeding from occurring near edges of a light distribution pattern inlight emitted from the respective diffraction gratings, even if thediffraction grating has a wavelength dependency. In this way, lighthaving a light distribution pattern in which color bleeding issuppressed is synthesized by a synthesis optical system, and a lightdistribution pattern of a low beam is formed. Therefore, it is possiblefor a low beam irradiated by the vehicle illumination lamp of thepresent invention to suppress color bleeding from appearing near edgesof a light distribution pattern.

Moreover, components advancing and passing through the diffractiongratings in the respective light emitting optical systems may besynthesized by the synthesis optical system, and may be projected to theprojection area. In this case, components advancing and passing throughthe respective diffraction gratings can be made a same color, even ifthe diffraction grating has a wavelength dependency such as describedabove. Therefore, it is possible to reduce pedestrians or the likeoutside a vehicle from being unnecessarily aware of the projection area.

Moreover, the vehicle illumination lamp of the present inventionincludes a light source, a diffraction grating for diffracting lightincident from the light source, and an optical element disposed, betweena projection area of light components advancing and passing through thediffraction grating and the diffraction grating, on an optical path ofthe light components, the optical element lowering an energy density oflight, in which light diffracted by the diffraction grating among thelight emitted from the diffraction grating is irradiated in apredetermined light distribution pattern.

The light components advancing and passing through the diffractiongrating correspond to the 0th-order light, and the light diffracted bythe diffraction grating corresponds to the high order diffracted light.Accordingly, the light advancing and passing through the diffractiongrating tends to have a high light intensity compared to a lightintensity of light diffracted by the diffraction grating. However, inthe case of the vehicle illumination lamp of the present invention, anoptical element for lowering an energy density of light is disposed,between a projection area of the light components corresponding to the0th-order light and the diffraction grating, on an optical path of thelight components. Therefore, even if a light intensity of the lightcomponents advancing and passing through the diffraction grating ishigher than a light intensity of light diffracted by the diffractiongrating, among light emitted from the diffraction grating, an energydensity of the light components can be lowered to less than that of theoptical element. Accordingly, it is possible to suppress the projectionarea of the light components advancing and passing through thediffraction grating from becoming noticeably brighter than a lightdistribution pattern by the light diffracted by the diffraction gratingamong the light emitted from the diffraction grating. In this way, thevehicle illumination lamp of the present invention can be easilyoperated compared to the case where not including the optical element.

Moreover, in the case where including an optical element for lowering anenergy density of light, a housing for accommodating the light sourceand the diffraction grating may be included, and the optical element maybe disposed in the housing. In this case, there will be a reduction ofthe light components corresponding to 0th-order light being emittedoutside the vehicle. Therefore, it is possible to suppress theprojection area of the light components corresponding to 0th-order lightfrom becoming noticeably bright outside the vehicle, and as a result ofthis, it is possible to suppress a driver, pedestrian or the like frombeing unnecessarily aware of the projection area.

Moreover, in the case where including an optical element for lowering anenergy density of light, the optical element may be a light shieldingelement or a light diffusing element. Accordingly, in the vehicleillumination lamp of the present invention, a light shielding element ora light diffusing element can be selected as the optical element, inaccordance with the type or the like of a vehicle mounted with thevehicle illumination lamp.

Moreover, in the case where including an optical element for lowering anenergy density of light, the projection area may be positioned outsideof the light distribution pattern. In this case, it is possible tosuppress a part of the light distribution pattern from becomingnoticeably bright, compared to the case where the projection area ispositioned within the light distribution pattern, and as a result ofthis, it can be easier to operate.

Moreover, in the case where including an optical element for lowering anenergy density of light, the light distribution pattern may have apredetermined light intensity distribution, and the projection area maybe included within an area, among the light distribution pattern, havinga light intensity of half a value or less of a highest light intensitywithin a light intensity distribution of the light diffracted by thediffraction grating.

In this case, it will be easy for the light intensity distribution ofthe light distribution pattern to be smoothly formed, on the basis of aposition having a highest light intensity within the light intensitydistribution of light diffracted by the diffraction grating, compared tothe case where the projection area is included in an area higher thanhalf a value of a highest light intensity within the light intensitydistribution of light diffracted by the diffraction grating.

Moreover, in the case where including an optical element for lowering anenergy density of light, a plurality of light emitting optical systemsincluding one light source and one diffraction grating may be included,a synthesis optical system for synthesizing light emitted from therespective light emitting optical systems may be included, the lightsources in the respective light emitting optical systems may emit lightof mutually different predetermined wavelengths, and the diffractiongratings in the respective light emitting optical systems may diffractlight from the light sources so that the light synthesized by thesynthesis optical system has the light distribution pattern.

In this case, in the respective light emitting optical systems, light ofa predetermined wavelength emitted from the light source is diffractedby the diffraction grating, and a light distribution pattern is formed.At this time, in the respective light emitting optical systems, sincelight diffracted by the diffraction grating has a predeterminedwavelength such as described above, it is possible to suppress colorbleeding from occurring near edges of a light distribution pattern inlight emitted from the respective diffraction gratings, even if thediffraction grating has a wavelength dependency. In this way, lighthaving a light distribution pattern in which color bleeding issuppressed is synthesized by a synthesis optical system, and a lightdistribution pattern of a low beam is formed. Therefore, it is possiblefor a low beam irradiated by the vehicle illumination lamp of thepresent invention to suppress color bleeding from appearing near edgesof a light distribution pattern.

Moreover, in the case where including an optical element for lowering anenergy density of light, light components advancing and passing throughthe diffraction gratings in the respective light emitting opticalsystems may be synthesized by the synthesis optical system, and theoptical element may lower an energy density of the light componentssynthesized by the synthesis optical system.

In this case, an irradiation area of the light components irradiated onthe optical element can be reduced, compared to the case where the lightcomponents advancing and passing through the diffraction gratings in therespective light emitting optical systems are not synthesized.Therefore, it is possible to suppress an energy density of lightdiffracted by the diffraction gratings, among the light emitted from thediffraction gratings, from being lowered by the optical element.

Moreover, a vehicle illumination lamp of the present invention includesa light source, and a diffraction grating for diffracting light incidentfrom the light source, in which a light distribution pattern having apredetermined light intensity distribution is formed by light diffractedby the diffraction grating and light advancing and passing through thediffraction grating, and a projection area of the light advancing andpassing through the diffraction grating within the light distributionpattern is positioned within an area having a light intensity higherthan half a value of a highest light intensity within a light intensitydistribution of the light diffracted by the diffraction grating.

The light advancing and passing through the diffraction gratingcorresponds to 0th-order light, and the light diffracted by thediffraction grating corresponds to high order diffracted light.Accordingly, the light advancing and passing through the diffractiongrating tends to have a high light intensity compared to a lightintensity of light diffracted by the diffraction grating. However, inthe case of the vehicle illumination lamp of the present invention, theprojection area of the light corresponding to 0th-order light ispositioned within an area having a light intensity higher than half avalue of a highest light intensity within a light intensity distributionof light corresponding to high order diffracted light. Therefore, evenif the light corresponding to 0th-order light is irradiated on theprojection area, it is possible to suppress the projection area frombecoming noticeably bright within the light distribution pattern.Therefore, the vehicle headlight of the present invention can be easilyoperated, compared to the case where the projection area is disposedoutside an area having a light intensity higher than half a value of ahighest light intensity within a light intensity distribution of thelight diffracted by the diffraction grating.

Moreover, in the case where the projection area of the lightcorresponding to 0th-order light is positioned within an area having alight intensity higher than half a value of a highest light intensity ina light intensity distribution of the light corresponding to high orderdiffracted light, it is preferable for the projection area to bepositioned to avoid a portion having a highest light intensity withinthe light intensity distribution. In this case, it is possible tosuppress the portion having a highest light intensity within the lightintensity distribution of light corresponding to high order diffractedlight from becoming excessively bright.

Moreover, in the case where the projection area of the lightcorresponding to 0th-order light is positioned within an area having alight intensity higher than half a value of a highest light intensity ina light intensity distribution of the light corresponding to high orderdiffracted light, it is preferable for the area to be a hot zone. Inthis case, while using the light corresponding to 0th-order light as alight distribution pattern, it is possible to suppress a projection areafrom becoming noticeably bright in this light distribution pattern.

Moreover, in the case where the projection area of the lightcorresponding to 0th-order light is positioned within an area having alight intensity higher than half a value of a highest light intensity ina light intensity distribution of the light corresponding to high orderdiffracted light, the light distribution pattern may be a lightdistribution pattern of a low beam.

Moreover, in the case where the projection area of the lightcorresponding to 0th-order light is positioned within an area having alight intensity higher than half a value of a highest light intensity ina light intensity distribution of the light corresponding to high orderdiffracted light, a plurality of light emitting optical systemsincluding one light source and one diffraction grating may be included,a synthesis optical system for synthesizing light emitted from therespective light emitting optical systems may be included, the lightsources in the respective light emitting optical systems may emit lightof mutually different predetermined wavelengths, and the diffractiongratings in the respective light emitting optical systems may emit lightfrom the light sources so that the light synthesized by the synthesisoptical system has the light distribution pattern.

In this case, light of a predetermined wavelength emitted from therespective light sources forms a light distribution pattern through thediffraction gratings. At this time, in the respective light emittingoptical systems, since light diffracted by the diffraction grating has apredetermined wavelength, it is possible to suppress color bleeding fromoccurring near edges of a light distribution pattern in light emittedfrom the respective diffraction gratings, even if the diffractiongratings have a wavelength dependency. In this way, light having a lightdistribution pattern in which color bleeding is suppressed issynthesized by a synthesis optical system, and a light distributionpattern is formed. Therefore, it is possible to suppress color bleedingfrom appearing near edges of a light distribution pattern.

Moreover, in the case where the projection area of the lightcorresponding to 0th-order light is positioned within an area having alight intensity higher than half a value of a highest light intensity ina light intensity distribution of the light corresponding to high orderdiffracted light, components advancing and passing through thediffraction grating in the respective light emitting optical systems maybe synthesized by the synthesis optical system, and may be irradiated onthe projection area. In this case, the 0th-order light passing throughthe respective diffraction gratings can be made a same color of white,even if the diffraction grating has a wavelength dependency such asdescribed above. Therefore, it is possible to reduce a driver,pedestrian or the like from being unnecessarily aware of the projectionarea, and it becomes easier to operate.

Moreover, the vehicle illumination lamp of the present inventionincludes a light source, and a diffraction grating for diffracting lightincident from the light source, in which light emitted from thediffraction grating is irradiated in a light distribution pattern havinga predetermined light intensity distribution, and in a projection areaof light advancing and passing through the diffraction grating among thelight distribution pattern, a light intensity of light diffracted by thediffraction grating and irradiated on the projection area is madesmaller than a light intensity of light irradiated to an outsideperipheral edge of the projection area.

The light advancing and passing through the diffraction gratingcorresponds to 0th-order light, and the light diffracted by thediffraction grating corresponds to high order diffracted light.Accordingly, the light advancing and passing through the diffractiongrating tends to have a high light intensity compared to a lightintensity of light diffracted by the diffraction grating. However, inthe case of the vehicle illumination lamp of the present invention, in aprojection area of light corresponding to 0th-order light, a lightintensity of light corresponding to high order diffracted light is madesmaller than a light intensity of light irradiated to an outsideperipheral edge of the projection area. Accordingly, even if the lightcorresponding to 0th-order light is irradiated on the projection area,it is possible to suppress the projection area being noticeably brightwithin the light distribution pattern. Therefore, the vehicleillumination lamp of the present invention can be easily operated,compared to the case where a light intensity of high order diffractedlight in the projection area is equal to or more than a light intensityof light irradiated to an outside peripheral edge of the projectionarea.

Moreover, in a projection area of light corresponding to 0th-orderlight, in the case where a light intensity of light corresponding tohigh order diffracted light is smaller than a light intensity of lightirradiated to an outside peripheral edge of the projection area, a totalvalue of the light intensity of light diffracted by the diffractiongrating and irradiated on the projection area and a light intensity oflight advancing and passing through the diffraction grating andirradiated on the projection area may be made lower than a highest lightintensity within a light intensity distribution of light diffracted bythe diffraction grating.

In this case, it will be easy for the light intensity distribution ofthe light distribution pattern to be smoothly formed, on the basis of aposition having a highest light intensity within the light intensitydistribution of light diffracted by the diffraction grating.

Moreover, in a projection area of light corresponding to 0th-orderlight, in the case where a light intensity of light corresponding tohigh order diffracted light is smaller than a light intensity of lightirradiated to an outside peripheral edge of the projection area, thelight intensity of light diffracted by the diffraction grating andirradiated on the projection area may be zero.

In this case, even in the case where a difference between the lightintensity of light corresponding to 0th-order light and the lightintensity of light corresponding to high order diffracted light islarge, it will be easy to suppress the projection area being noticeablybright within the light distribution pattern, and to form a smooth lightintensity distribution as the whole light distribution pattern.

Moreover, in a projection area of light corresponding to 0th-orderlight, in the case where a light intensity of light corresponding tohigh order diffracted light is smaller than a light intensity of lightirradiated to an outside peripheral edge of the projection area, theprojection area may be included within an area having a light intensityhigher than half a value of a highest light intensity within a lightintensity distribution of light diffracted by the diffraction grating.

In this case, it is possible to suppress the projection area beingnoticeably bright within the light distribution pattern, compared to thecase where the projection area is included in an area of half a value orless of a highest light intensity within a light intensity distributionof light diffracted by the diffraction grating.

Moreover, in a projection area of light corresponding to 0th-orderlight, in the case where a light intensity of light corresponding tohigh order diffracted light is smaller than a light intensity of lightirradiated to an outside peripheral edge of the projection area, theprojection area may include a position having a highest light intensitywithin the light intensity distribution of light diffracted by thediffraction grating.

In this case, the brightest area within the light distribution patternwill be mostly unchanged, regardless of whether or not the lightintensity of light corresponding to 0th-order light is large.Accordingly, a light intensity distribution of the light distributionpattern can be more smoothly formed, on the basis of a position having ahighest light intensity within the light intensity distribution of lightdiffracted by the diffraction grating.

Moreover, in a projection area of light corresponding to 0th-orderlight, in the case where a light intensity of light corresponding tohigh order diffracted light is smaller than a light intensity of lightirradiated to an outside peripheral edge of the projection area, aplurality of light emitting optical systems including one light sourceand one diffraction grating may be included, a synthesis optical systemfor synthesizing light emitted from the respective light emittingoptical systems may be included, the light sources in the respectivelight emitting optical systems may emit light of mutually differentpredetermined wavelengths, and the diffraction gratings in therespective light emitting optical systems may emit light from the lightsources so that the light synthesized by the synthesis optical systemhas the light distribution pattern.

In this case, in the respective light emitting optical systems, light ofa predetermined wavelength emitted from the light source is diffractedby the diffraction grating, and a light distribution pattern is formed.At this time, in the respective light emitting optical systems, sincelight diffracted by the diffraction grating has a predeterminedwavelength such as described above, it is possible to suppress colorbleeding from occurring near edges of a light distribution pattern inlight emitted from the respective diffraction gratings, even if thediffraction grating has a wavelength dependency. In this way, lighthaving a light distribution pattern in which color bleeding issuppressed is synthesized by a synthesis optical system, and a lightdistribution pattern is formed. Therefore, it is possible to suppresscolor bleeding from appearing near edges of a light distribution patternformed by the vehicle illumination lamp of the present invention.

Moreover, in a projection area of light corresponding to 0th-orderlight, in the case where a light intensity of light corresponding tohigh order diffracted light is smaller than a light intensity of lightirradiated to an outside peripheral edge of the projection area,components advancing and passing through the diffraction gratings in therespective light emitting optical systems may be synthesized by thesynthesis optical system, and may be irradiated on the projection area.In this case, components advancing and passing through the respectivediffraction gratings can be made a same color, even if the diffractiongrating has a wavelength dependency such as described above. Therefore,it is possible to reduce a driver, pedestrian or the like from beingunnecessarily aware of the projection area, and it becomes easier tooperate.

Moreover, in a projection area of light corresponding to 0th-orderlight, in the case where a light intensity of light corresponding tohigh order diffracted light is smaller than a light intensity of lightirradiated to an outside peripheral edge of the projection area, aplurality of light emitting optical systems including one light sourceand one diffraction grating may be included, the light sources in therespective light emitting optical systems may emit light of mutuallydifferent predetermined wavelengths, and the diffraction gratings in therespective light emitting optical systems may emit light from the lightsources so as to have the light distribution pattern at a positionseparated a predetermined distance from a vehicle.

In this case, since the synthesis optical system is not used, it ispossible to form a simple configuration.

Moreover, a vehicle headlight of the present invention includes at leasttwo light emitting optical systems having a light source and adiffraction grating, in which the light sources in the respective lightemitting optical systems emit light of mutually different predeterminedwavelengths, and the diffraction gratings in the respective lightemitting optical systems diffract light from the light sources so lightin which the lights emitted from the respective light emitting opticalsystems are synthesized has a light distribution pattern for nightillumination.

Since this vehicle headlight can form a light distribution pattern of alow beam without using a shade similar to the vehicle headlightdescribed in Patent Document 1, it is possible to be reduced in sizecompared to a vehicle headlight using a shade similar to the vehicleheadlight of Patent Document 1. In the respective light emitting opticalsystems, light of a predetermined wavelength emitted from the lightsource is diffracted by the diffraction grating, and a lightdistribution pattern is formed. At this time, in the respective lightemitting optical systems, since light diffracted by the diffractiongrating has a predetermined wavelength such as described above, it ispossible to suppress color bleeding from occurring near edges of a lightdistribution pattern in light emitted from the respective diffractiongratings, even if the diffraction grating has a wavelength dependency.In this way, light having a light distribution pattern in which colorbleeding is suppressed is synthesized, and a light distribution patternfor night illumination such as a low beam or a high beam is formed.Therefore, it is possible for a low beam irradiated by the vehicleheadlight of the present invention to suppress color bleeding fromappearing near edges of a light distribution pattern, compared to thecase where white light is diffracted by a diffraction grating such as inPatent Document 1. Note that, the synthesis of the lights emitted fromthe respective light emitting optical systems may be performed insidethe vehicle headlight or outside the vehicle headlight.

Moreover, in the case where including at least two light emittingoptical systems having a light source and a diffraction grating, it ispreferable for at least three light emitting optical systems to beincluded.

In this case, light of three primary colors can be used. Therefore,light of a desired color can be irradiated, by adjusting a lightintensity of the lights emitted from the respective light emittingoptical systems.

Further, in the case where including at least two light emitting opticalsystems having a light source and a diffraction grating, it ispreferable to further include a synthesis optical system for combiningand synthesizing external shapes of lights emitted from the respectivelight emitting optical systems, and in this case, the synthesis opticalsystem may have at least one optical filter, and the optical filter maysynthesize light passing through the optical filter and light reflectingthe optical filter.

In this case, since the lights emitted from the respective lightemitting optical systems are synthesized by the synthesis optical systemand then emitted from the vehicle headlight, it is possible to furthersuppress color bleeding from appearing near edges of an irradiated lightdistribution pattern regardless of the distance from a vehicle.Moreover, since the lights emitted from the respective light emittingoptical systems are synthesized by the synthesis optical system and thenemitted from the vehicle headlight, the emission portion of the vehicleheadlight where synthesized light is emitted can be made small, comparedto the case where the lights emitted from the respective light emittingoptical systems are emitted from the vehicle headlight without beingsynthesized, and synthesized outside the vehicle headlight, and thedegree of freedom of the design can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a vehicle thatincludes a vehicle headlight according to a first embodiment of thepresent invention.

FIG. 2 is an enlarged view of an optical system unit of the vehicleheadlight of FIG. 1 .

FIG. 3 is a figure showing a light distribution pattern of a low beam.

FIG. 4 is a figure showing a projection area of 0th-order light.

FIG. 5 is a figure showing, similar to FIG. 2 , an optical system unitof a vehicle headlight according to a second embodiment of the presentinvention.

FIG. 6 is a cross-sectional view schematically showing a vehicle thatincludes a vehicle headlight according to a third embodiment of thepresent invention.

FIG. 7 is a figure showing, similar to FIG. 2 , an optical system unitof a vehicle headlight according to a fourth embodiment of the presentinvention.

FIG. 8 is a figure showing a light distribution pattern of a low beamand a light distribution pattern of light for visually recognizing asign.

FIG. 9 is a figure showing a light distribution pattern of a high beam.

FIG. 10 is a cross-sectional view schematically showing a vehicle thatincludes a vehicle headlight according to a fifth embodiment of thepresent invention.

FIG. 11 is an enlarged view of an optical system unit of the vehicleheadlight of FIG. 10 .

FIG. 12 is a figure showing a light distribution pattern of a low beamand a light intensity distribution of this light distribution pattern.

FIG. 13 is a figure showing, similar to FIG. 11 , an optical system unitof a vehicle headlight according to a sixth embodiment of the presentinvention.

FIG. 14 is a figure showing a light distribution pattern of a low beamand a light distribution pattern of light for visually recognizing asign.

FIG. 15 is a figure showing a light distribution pattern of a low beam,and a light intensity distribution of this light distribution pattern.

FIG. 16 is a figure showing a light distribution pattern of a low beamof the case where a 0th-order light beam is unirradiated, and a lightintensity distribution of this light distribution pattern.

FIG. 17 is a cross-sectional view schematically showing a vehicle thatincludes a vehicle headlight according to a ninth embodiment of thepresent invention.

FIG. 18 is an enlarged view of an optical system unit of FIG. 17 .

FIG. 19A and FIG. 19B are figures showing a light distribution pattern.

FIG. 20 is a figure showing, similar to FIG. 18 , an optical system unitof a vehicle headlight according to a tenth embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, aspects for implementing a vehicle illumination lamp and avehicle headlight according to the present invention will be exemplifiedalong with accompanying figures. The embodiments exemplified below areintended to facilitate understanding of the present invention, and arenot intended to limit the present invention. The present invention canbe modified and improved from the following embodiments, withoutdeparting from the spirit of the present invention.

First, a configuration of a vehicle illumination lamp of the presentembodiment will be described.

First Embodiment

FIG. 1 is a cross-sectional view schematically showing a vehicle thatincludes a vehicle headlight according to the present embodiment. Thevehicle headlight 1 of the present embodiment includes a housing 10, anda lamp unit 20.

The housing 10 includes a lamp housing 11, a front cover 12, and a backcover 13 as the main components. The front of the lamp housing 11 isopen, and the front cover 12 is fixed to the lamp housing 11 so as toclose this opening. An opening smaller than the front is formed behindthe lamp housing 11, and the back cover 13 is fixed to the lamp housing11 so as to close this opening.

A space formed by the lamp housing 11, the front cover 12 closing theopening in front of the lamp housing 11, and the back cover 13 closingthe opening behind the lamp housing 11, is a lamp chamber R, and thelamp unit 20 is accommodated within this lamp chamber R.

The lamp unit 20 includes a heat sink 30, a cooling fan 40, and anoptical system unit 50 as the main components. Note that, the lamp unit20 is fixed to the housing 10 by a configuration that is notillustrated.

The heat sink 30 has a metal base plate 31 extending in a substantiallyhorizontal direction, and a plurality of radiating fins 32 areintegrally provided with the base plate 31 on a lower surface side ofthe base plate 31. The cooling fan 40 is disposed with a gap from theradiating fins 32, and is fixed to the heat sink 30. The heat sink 30 iscooled by airflow by rotation of the cooling fan 40.

The optical system unit 50 is disposed on an upper surface of the baseplate 31 in the heat sink 30. The optical system unit 50 includes afirst light emitting optical system 51R, a second light emitting opticalsystem 51G, a third light emitting optical system 51B, a synthesisoptical system 55, and a cover 59.

FIG. 2 is an enlarged view of the optical system unit of the vehicleheadlight shown in FIG. 1 . As shown in FIG. 2 , the first lightemitting optical system 51R includes a light source 52R, a collimatorlens 53R, and a diffraction grating 54R. The light source 52R is a laserelement that emits laser light having a predetermined wavelength, and inthe present embodiment, emits red laser light having a peak wavelengthof power of, for example, 638 nm. The optical system unit 50 has acircuit board that is not illustrated, and the light source 52R ismounted on this circuit board. Power is supplied to the light source 52Rthrough this circuit board.

The collimator lens 53R is a lens that collimates a fast axis directionand a slow axis direction of laser light emitted from the light source52R. A collimator lens that collimates a fast axis direction and acollimator lens that collimates a slow axis direction of laser light maybe separately provided.

The diffraction grating 54R emits laser light emitted from thecollimator lens 53R so as to have a predetermined light distributionpattern. Specifically, the diffraction grating 54R, in the synthesisoptical system 55 described later, diffracts laser light incident fromthe collimator lens 53R so that lights respectively emitted from thefirst light emitting optical system 51R, the second light emittingoptical system 51G, and the third light emitting optical system 51B havea light distribution pattern of a low beam L. A light intensitydistribution is also included in this light distribution pattern.Accordingly, the diffraction grating 54R of the present embodimentdiffracts laser light incident from the collimator lens 53R, so as tohave a light intensity distribution based on a light intensitydistribution of a light distribution pattern of the low beam L, alongwith laser light emitted from the diffraction grating 54R having a sameexternal shape as an external shape of a light distribution pattern ofthe low beam L.

This light diffracted by the diffraction grating 54R is high orderdiffracted light having an order of 1 or more, and in addition to thishigh order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54R without being diffracted is emittedfrom the diffraction grating 54R. Namely, light emitted from thediffraction grating 54R includes high order diffracted light that is alight component diffracted by the diffraction grating 54R, and 0th-orderlight that is a light component advancing and passing through thediffraction grating 54R. In the present embodiment, 0th-order lightadvancing and passing through the diffraction grating 54R is emittedfrom the diffraction grating 54R, so that a projection area of a0th-order light beam LC emitted from the synthesis optical system 55described later is positioned within a predetermined range below a lightdistribution pattern of the low beam L. For example, the diffractiongrating 54R may diffract laser light incident from the collimator lens53R, so that high order diffracted light is emitted in a state displacedabove a direction of 0th-order light advancing through the diffractiongrating 54R.

In this way, a red component of high order diffracted light among thelow beam L, and a red component of 0th-order light among the 0th-orderlight beam LC are emitted from the first light emitting optical system51R. In the present embodiment, a red component of high order diffractedlight emitted from the first light emitting optical system 51R is set asfirst light L_(R), and a red component of 0th-order light is set asfirst 0th-order light LC_(R).

The second light emitting optical system 51G includes a light source52G, a collimator lens 53G, and a diffraction grating 54G, and the thirdlight emitting optical system 51B includes a light source 52B, acollimator lens 53B, and a diffraction grating 54B. The light sources52G and 52B are respectively laser elements that emit laser light havinga predetermined wavelength, and in the present embodiment, the lightsource 52G emits green laser light having a peak wavelength of power of,for example, 515 nm, and the light source 52B emits blue laser lighthaving a peak wavelength of power of, for example, 445 nm. Moreover, thelight sources 52G and 52B are respectively mounted on the circuit board,and power is supplied to the light sources 52G and 52B via this circuitboard.

The collimator lens 53G is a lens that collimates a fast axis directionand a slow axis direction of laser light emitted from the light source52G, and the collimator lens 53B is a lens that collimates a fast axisdirection and a slow axis direction of laser light emitted from thelight source 52B. In the collimator lenses 53G and 53B, a collimatorlens that collimates a fast axis direction and a collimator lens thatcollimates a slow axis direction of laser light may be separatelyprovided, similar to the collimator lens 53R.

The diffraction grating 54G emits laser light emitted from thecollimator lens 53G so as to have a predetermined light distributionpattern, and the diffraction grating 54B emits laser light emitted fromthe collimator lens 53B so as to have a predetermined light distributionpattern. Specifically, the diffraction gratings 54G and 54B, in thesynthesis optical system 55, respectively diffract laser light incidentfrom the collimator lenses 53G and 53B so that lights respectivelyemitted from the first light emitting optical system 51R, the secondlight emitting optical system 51G, and the third light emitting opticalsystem 51B have a light distribution pattern of the low beam L. A lightintensity distribution is also included in the light distributionpattern, such as described above. Accordingly, the diffraction gratings54G and 54B of the present embodiment respectively diffract laser lightincident from the collimator lenses 53G and 53B, so as to have a lightintensity distribution based on a light intensity distribution of alight distribution pattern of the low beam L, along with laser lightrespectively emitted from the diffraction gratings 54G and 54B having asame external shape as an external shape of a light distribution patternof the low beam L.

The light diffracted by this diffraction grating 54G is high orderdiffracted light having an order of 1 or more, and in addition to thishigh order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54G without being diffracted is emittedfrom the diffraction grating 54G. Namely, light emitted from thediffraction grating 54G includes high order diffracted light that is alight component diffracted by the diffraction grating 54G, and 0th-orderlight that is a light component advancing and passing through thediffraction grating 54G. In the present embodiment, 0th-order lightadvancing and passing through the diffraction grating 54G is emittedfrom the diffraction grating 54G, so that a projection area of a0th-order light beam LC emitted from the synthesis optical system 55described later is positioned within a predetermined range below a lightdistribution pattern of the low beam L. For example, the diffractiongrating 54G may diffract laser light incident from the collimator lens53G, so that high order diffracted light is emitted in a state displacedabove a direction of 0th-order light advancing through the diffractiongrating 54G.

Similarly, this light diffracted by the diffraction grating 54B is highorder diffracted light having an order of 1 or more, and in addition tothis high order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54B without being diffracted is emittedfrom the diffraction grating 54B. Namely, light emitted from thediffraction grating 54B includes high order diffracted light that is alight component diffracted by the diffraction grating 54G, and 0th-orderlight that is a light component advancing and passing through thediffraction grating 54B. In the present embodiment, 0th-order lightadvancing and passing through the diffraction grating 54B is emittedfrom the diffraction grating 54B, so that a projection area of a0th-order light beam LC emitted from the synthesis optical system 55described later is positioned within a predetermined range below a lightdistribution pattern of the low beam L. For example, the diffractiongrating 54B may diffract laser light incident from the collimator lens53B, so that high order diffracted light is emitted in a state displacedabove a direction of 0th-order light advancing through the diffractiongrating 54B.

In this way, a green component of high order diffracted light among thelow beam L, and a green component of 0th-order light among the 0th-orderlight beam LC are emitted from the second light emitting optical system51G. Moreover, a blue component of high order diffracted light among thelow beam L, and a blue component of 0th-order light among the 0th-orderlight beam LC are emitted from the third light emitting optical system51B. In the present embodiment, a green component of high orderdiffracted light emitted from the second light emitting optical system51G is set as second light L_(G), a green component of 0th-order lightis set as second 0th-order light LC_(G), a blue component of high orderdiffracted light emitted from the third light emitting optical system51B is set as third light L_(B), and a blue component of 0th-order lightis set as third 0th-order light LC_(B). Therefore, in the presentembodiment, the first light L_(R) has a longest wavelength, and thewavelength becomes shorter in the order of the second light L_(G) andthe third light L_(B). Similarly, the first 0th-order light LC_(R) has alongest wavelength, and the wavelength becomes shorter in the order ofthe second 0th-order light LC_(G) and the third 0th-order light LC_(B).

Note that, a light intensity distribution based on a light intensitydistribution of a light distribution pattern of the low beam L meansthat the light intensities of lights respectively emitted from thediffraction gratings 54R, 54G, and 54B are high, at a portion where alight intensity in a light distribution pattern of the low beam L ishigh.

The synthesis optical system 55 includes a first optical element 55 fand a second optical element 55 s. The first optical element 55 f is anoptical element that synthesizes the first light L_(R) emitted from thefirst light emitting optical system 51R and the second light L_(G)emitted from the second light emitting optical system 51G. Moreover, thefirst optical element 55 f is also an optical element that synthesizesthe first 0th-order light LC_(R) emitted from the first light emittingoptical system 51R and the second 0th-order light LC_(G) emitted fromthe second light emitting optical system 51G. In the present embodiment,the first optical element 55 f synthesizes the first light L_(R) and thesecond light L_(G) by transmitting the first light L_(R) and reflectingthe second light L_(G), and synthesizes the first 0th-order light LC_(R)and the second 0th-order light LC_(G) by transmitting the first0th-order light LC_(R) and reflecting the second 0th-order light LC_(G).

The second optical element 55 s is an optical element that synthesizesthe first light L_(R) and the second light L_(G) synthesized by thefirst optical element 55 f and the third light L_(B) emitted from thethird light emitting optical system 51B. Moreover, the second opticalelement 55 s is also an optical element that synthesizes the first0th-order light LC_(R) and the second 0th-order light LC_(G) synthesizedby the first optical element 55 f and the third 0th-order light LC_(B)emitted from the third light emitting optical system 51B. In the presentembodiment, the second optical element 55 s synthesizes the first lightL_(R), the second light L_(G), and the third light L_(B) by transmittingthe first light L_(R) and the second light L_(G) synthesized by thefirst optical element 55 f and reflecting the third light L_(B).Moreover, the second optical element 55 s synthesizes the first0th-order light LC_(R), the second 0th-order light LC_(G), and the third0th-order light LC_(B) by transmitting the first 0th-order light LC_(R)and the second 0th-order light LC_(G) synthesized by the first opticalelement 55 f and reflecting the third 0th-order light LC_(B).

An optical filter, in which an oxide film is layered on a glasssubstrate, can be included as such a first optical element 55 f andsecond optical element 55 s. By controlling the type and thickness ofthis oxide film, it is possible to form a configuration that transmitslight having a wavelength longer than a predetermined wavelength, andreflects light having a wavelength shorter than this wavelength.

In this way, the low beam L is emitted, by having the first light L_(R),the second light L_(G), and the third light L_(B) synthesized, and the0th-order light beam LC is emitted, by having the first 0th-order lightLC_(R), the second 0th-order light LC_(G), and the third 0th-order lightLC_(B) synthesized, from the synthesis optical system 55.

The cover 59 is fixed on the base plate 31 of the heat sink 30. Thecover 59 has a substantially rectangular shape, and is made, forexample, of a metal such as aluminum. The first light emitting opticalsystem 51R, the second light emitting optical system 51G, the thirdlight emitting optical system 51B, and the synthesis optical system 55are disposed in a space inside the cover 59. Moreover, an opening 59Hthrough which light emitted from the synthesis optical system 55 can betransmitted is formed in front of the cover 59. Note that, it ispreferable for an inner wall of the cover 59 to have a light absorptanceby black alumite processing or the like. By making an inner wall of thecover 59 have a light absorptance, it is possible to suppress lightirradiated on the inner wall of the cover 59 from being reflected andemitted in an unintended direction from the opening 59H, due tounintended reflection or refraction or the like.

Next, the emission of light by the vehicle headlight 1 of the presentembodiment will be described.

First, by supplying power from a power source that is not illustrated,laser light is emitted from the respective light sources 52R, 52G, and52B. As described above, red laser light is emitted from the lightsource 52R, green laser light is emitted from the light source 52G, andblue laser light is emitted from the light source 52B. The respectivelaser lights are collimated by collimator lenses 53R, 53G, and 53B, andafterwards are incident on the diffraction gratings 54R, 54G, and 54B.Then, as described above, the respective laser lights are diffracted bythe diffraction gratings 54R, 54G, and 54B, the first light L_(R) thatis a red component of light of a light distribution pattern of the lowbeam L is emitted from the first light emitting optical system 51R, thesecond light L_(G) that is a green component of light of a lightdistribution pattern of the low beam L is emitted from the second lightemitting optical system 51G, and the third light L_(B) that is a bluecomponent of light of a light distribution pattern of the low beam L isemitted from the third light emitting optical system 51B. Moreover, asdescribed above, the first 0th-order light LC_(R) that is a redcomponent of 0th-order light is emitted from the first light emittingoptical system 51R, the second 0th-order light LC_(G) that is a greencomponent of 0th-order light is emitted from the second light emittingoptical system 51G, and the third 0th-order light LC_(B) that is a bluecomponent of the 0th-order light is emitted from the third lightemitting optical system 51B, as 0th-order lights advancing and passingthrough the diffraction gratings 54R, 54G, and 54B.

In the synthesis optical system 55, first, the first light L_(R) and thesecond light L_(G) are synthesized and emitted by the first opticalelement 55 f, and the first 0th-order light LC_(R) and the second0th-order light LC_(G) are synthesized and emitted by the first opticalelement 55 f. The first light L_(R) and the second light L_(G)synthesized by the first optical element 55 f are synthesized with thethird light L_(B) by the second optical element 55 s, and the first0th-order light LC_(R) and the second 0th-order light LC_(G) synthesizedby the first optical element 55 f are synthesized with the third0th-order light LC_(B) by the second optical element 55 s. At this time,since the respective lights L_(R), L_(G), and L_(B) have an externalshape the same as the external shape of the low beam L, the externalshapes of the respective lights L_(R), L_(G), and L_(B) will besynthesized by matching each other. In addition, since the externalshapes of the respective 0th-order lights LC_(R), LC_(G), and LC_(B) arealso the same, the external shapes of the respective 0th-order lightsLC_(R), LC_(G), and LC_(B) will be synthesized by matching each other.Namely, the positions of each of the light emitting optical systems andthe synthesis optical system are finely adjusted, so that the externalshape of the first light L_(R), the external shape of the second lightL_(G), and the external shape of the third light L_(B), and also theexternal shape of the first 0th-order light LC_(R), the external shapeof the second 0th-order light LC_(G), and the external shape of thethird 0th-order light LC_(B), are combined by the synthesis opticalsystem such as described above.

In this way, light in which the red first light L_(R), the green secondlight L_(G), and the blue third light L_(B) are synthesized becomeswhite light. Moreover, light in which the red first 0th-order lightLC_(R), the green second 0th-order light LC_(G), and the blue third0th-order light LC_(B) are synthesized becomes white 0th-order light.Note that, since the first light L_(R), the second light L_(G), and thethird light L_(B) are light intensity distributions based on a lightintensity distribution of a light distribution pattern of the low beam Lsuch as described above, white light in which these lights aresynthesized will become a light intensity distribution of the low beamL.

In this way, synthesized white light is emitted from the opening 59H ofthe cover 59, and this light is emitted from the vehicle headlight 1 tothe front of the vehicle via the front cover 12. Since this light has alight distribution pattern of the low beam L, the irradiated lightbecomes the low beam L.

FIG. 3 is a figure showing a light distribution pattern of the low beamL in the present embodiment. In FIG. 3 , S shows a horizontal line, anda light distribution pattern is shown by a bold line. Among a lightdistribution pattern PTN_(L) of this low beam L, an area LA1 is an areahaving a highest light intensity, and the light intensity decreases inthe order of an area LA2 and an area LA3. Namely, the respectivediffraction gratings 54R, 54G, and 54B diffract light so thatsynthesized light forms a light distribution pattern including a lightintensity distribution of the low beam L.

Further, synthesized white 0th-order light is emitted from the opening59H of the cover 59, this light is emitted from the vehicle headlight 1to the front lower side of the vehicle via the front cover 12, and isprojected to a projection area on a lower side of a light distributionpattern of the low beam L.

FIG. 4 is a diagram showing a projection area of 0th-order light. Asshown in FIG. 4 , a projection area AR of the present embodiment ispositioned within a range RNG in which a field of view of a driver of anautomobile is obstructed by the hood of the vehicle. Namely, theprojection area AR is positioned within a range RNG that is a blind spotof a driver of an automobile. Note that, road surface illuminance in anarea other than the projection area AR of 0th-order light, among therange RNG that is a blind spot of a driver of an automobile, isapproximately 5 lx or less.

Incidentally, the hologram element of the vehicle headlight in PatentDocument 1 is calculated, so that 1st-order light for forming a lightdistribution pattern of a low beam is irradiated in front of thevehicle, and 0th-order light is irradiated toward the front other thanthe light distribution pattern of this low beam light. Accordingly, inthe vehicle headlight in Patent Document 1, the possibility of 0th-orderlight causing glare can be prevented. 0th-order light tends to have ahigh light intensity compared to a light intensity of high orderdiffracted light having an order of 1 or more. However, in the vehicleheadlight described in Patent Document 1, while the 0th-order lightemitted from the hologram element is light other than a lightdistribution pattern of the low beam, the 0th-order light is emittedtoward the front of the vehicle. For this reason, there is a demand tohave an easier operation.

Accordingly, the vehicle headlight 1 of the present embodiment includeslight sources 52R, 52G, and 52B, and diffraction gratings 54R, 54G, and54B that diffract light incident from the light sources 52R, 52G, and52B.

The projection area AR, on which is projected 0th-order light that is acomponent advancing and passing through the diffraction gratings 54R,54G, and 54B from among light incident on the diffraction gratings 54R,54G, and 54B, is lower than a light distribution pattern diffracted andirradiated by the diffraction gratings 54R, 54G, and 54B. In addition tothis, the projection area AR is positioned within a range RNG in which afield of view of a driver of an automobile is obstructed by theautomobile.

Therefore, the vehicle headlight 1 of the present embodiment cansuppress a reduction in a driver's ability to pay attention due to the0th-order light having a high light intensity compared to a lightintensity of high order light from 1st-order light onwards. Accordingly,the vehicle headlight 1 of the present embodiment can be easilyoperated, compared to the case where 0th-order light is in a field ofview of a driver of an automobile.

Note that, light diffracted by the diffraction gratings 54R, 54G, and54B, in the present embodiment, is irradiated in a light distributionpattern of the low beam L. Since the light distribution pattern PTN_(L)of the low beam L has a light intensity distribution in which a centralportion of the light distribution pattern PTN_(L) is bright andperipheral portions other than the central portion are relatively dark,such as shown in FIG. 3 , a natural light distribution pattern can beirradiated that does not provide a driver with a sense of discomfort.

Therefore, since the vehicle headlight 1 of the present embodiment canform the light distribution pattern PTN_(L) of the low beam L withoutusing a shade, it is possible to reduce in size compared to a vehicleheadlight using a shade.

Moreover, the vehicle headlight 1 of the present embodiment has aplurality of light emitting optical systems including one light sourceand one diffraction grating. Namely, the vehicle headlight 1 has a firstlight emitting optical system 51R including one light source 52R and onediffraction grating 54R, a second light emitting optical system 51Gincluding one light source 52G and one diffraction grating 54G, and athird light emitting optical system 51B including one light source 52Band one diffraction grating 54B. In addition to this, the vehicleheadlight 1 of the present embodiment further includes a synthesisoptical system 55 that synthesizes lights emitted from the respectivelight emitting optical systems 51R, 51G, and 51B. Also, the respectivelight sources 52R, 52G, and 52B emit light of mutually differentpredetermined wavelengths, and the respective diffraction gratings 54R,54G, and 54B diffract light from the light sources 52R, 52G, and 52B sothat light synthesized by the synthesis optical system 55 has the lightdistribution pattern PTN_(L) of the low beam L.

In this case, light having a predetermined wavelength emitted from therespective light sources 52R, 52G, and 52B is diffracted by thediffraction gratings 54R, 54G, and 54B, and the light distributionpattern PTN_(L) is formed. At this time, in the respective lightemitting optical systems 51R, 51G, and 51B, since light diffracted bythe diffraction gratings 54R, 54G, and 54B has a predeterminedwavelength, it is possible to suppress color bleeding from occurringnear edges of the light distribution pattern PTN_(L) in the lightsemitted from the respective diffraction gratings 54R, 54G, and 54B, evenif the diffraction gratings 54R, 54G, and 54B have a wavelengthdependency. In this way, light having a light distribution pattern inwhich color bleeding is suppressed is synthesized by the synthesisoptical system 55, and the light distribution pattern PTN_(L) of the lowbeam L is formed. Therefore, the low beam L irradiated by the vehicleheadlight 1 of the present embodiment can suppress color bleeding fromappearing near edges of the light distribution pattern PTN_(L).

Moreover, in the vehicle headlight 1 of the present embodiment, the0th-order lights LC_(R), LC_(G), and LC_(B) advancing and passingthrough the respective diffraction gratings 54R, 54G, and 54B aresynthesized by the synthesis optical system 55, and projected to theprojection area AR. In this case, even if the diffraction gratings 54R,54G, and 54B have a wavelength dependency such as described above, the0th-order lights LC_(R), LC_(G), and LC_(B) passing through therespective diffraction gratings 54R, 54G, and 54B can be made a samewhite color. Therefore, in the vehicle headlight 1 of the presentembodiment, it is possible to reduce pedestrians or the like outside avehicle from being unnecessarily aware of the projection area AR.

Second Embodiment

Next, a second embodiment of the present invention will be described indetail with reference to FIG. 5 . Note that, overlapping descriptionsattached with the same reference numerals, except for particulardescriptions, will be omitted for constituent elements the same orequivalent to those of the first embodiment.

FIG. 5 is a figure showing, similar to FIG. 2 , an optical system unitof a vehicle headlight according to the present embodiment. As shown inFIG. 5 , the optical system unit 50 of the vehicle headlight of thepresent embodiment is different to the optical system unit 50 of thefirst embodiment for the point of not including the synthesis opticalsystem 55, and emitting the respective lights emitted from the firstlight emitting optical system 51R, the second light emitting opticalsystem 51G, and the third light emitting optical system 51B from thecover 59, in a state where not synthesized. In the present embodiment,the first light emitting optical system 51R, the second light emittingoptical system 51G, and the third light emitting optical system 51B havean irradiation direction of light on an opening 59H side of the cover59.

In the present embodiment, similar to the first embodiment, in thediffraction grating 54R of the first light emitting optical system 51R,the diffraction grating 54G of the second light emitting optical system51G, and the diffraction grating 54B of the third light emitting opticalsystem 51B, respectively, light is emitted so that synthesized lightforms a light distribution pattern of the low beam L.

Namely, the first light L_(R) emitted from the diffraction grating 54R,the second light L_(G) emitted from the diffraction grating 54G, and thethird light L_(B) emitted from the diffraction grating 54B arerespectively emitted from the opening 59H of the cover 59, andirradiated to the outside of the vehicle headlight via the front cover12. Moreover, the first 0th-order light LC_(R) emitted from thediffraction grating 54R, the second 0th-order light LC_(G) emitted fromthe diffraction grating 54G, and the third 0th-order light LC_(B)emitted from the diffraction grating 54B are respectively emitted fromthe opening 59H of the cover 59, and irradiated to the outside of thevehicle headlight via the front cover 12. At this time, the first lightL_(R), the second light L_(G), and the third light L_(B) are irradiatedso that the external shapes of the respective light distributionpatterns substantially match each other at a focal position separated apredetermined distance from the vehicle. This distance from the vehicleis, for example, 25 m. Also, the first 0th-order light LC_(R), thesecond 0th-order light LC_(G), and the third 0th-order light LC_(B) areirradiated so that the external shapes of the respective lightdistribution patterns substantially match each other within the rangeRNG that is a blind spot of a driver of an automobile. Namely, in thepresent embodiment, the irradiation directions of light of the firstlight emitting optical system 51R, the second light emitting opticalsystem 51G, and the third light emitting optical system 51B are finelyadjusted, so that the external shapes match each other such as describedabove.

According to the vehicle headlight of the present embodiment, since thesynthesis optical system 55 of the first embodiment is not used, it ispossible to form a simple configuration. Moreover, according to thevehicle headlight 1 of the present embodiment, similar to the firstembodiment, since 0th-order light having a high light intensity comparedto a light intensity of high order light from 1st-order light onwards isirradiated within the range RNG that is a blind spot of a driver of anautomobile, it is possible to suppress a reduction in a driver's abilityto pay attention. Note that, the external shape of the first lightL_(R), the external shape of the second light L_(G), and the externalshape of the third light L_(B), and also the external shape of the first0th-order light LC_(R), the external shape of the second 0th-order lightLC_(G), and the external shape of the third 0th-order light LC_(B), ofthe present embodiment tend to slightly deviate from each other exceptfor at the focal position. However, when compared with light obtained byhaving white light incident on one diffraction grating, it is possibleto suppress this deviation of the external shapes. Therefore, accordingto the present embodiment, a vehicle headlight can be realized that iscapable of suppressing color bleeding while being reduced in size.

Note that, in the first and second embodiments, there is included thefirst light emitting optical system that emits a red component of thefirst light L_(R), the second light emitting optical system that emits agreen component of the second light L_(G), and the third light emittingoptical system that emits a blue component of the third light L_(B).However, in the first and second embodiments, the lights emitted fromthe light sources respectively included in the three light emittingoptical systems are not limited to red, green, and blue, as long as theyhave respectively different predetermined wavelengths.

Moreover, the number of light emitting optical systems may be one ortwo. In addition, the number of light emitting optical systems may bethree or more. In this case, for example, a fourth light emittingoptical system that emits a yellow component of light of the low beam Lmay be provided. In this case, in addition to the red, green, and bluelight emitting optical systems, the fourth light emitting optical systemmay emit a yellow component of light of the low beam L. Moreover, in thecase where a light intensity of a part of red, green, and blue is low,the fourth light emitting optical system may emit a color component oflight the same as the color with a low light intensity.

Moreover, in the first and second embodiments, a white balanceadjustment circuit may be further provided. This white balanceadjustment circuit can achieve a desired white balance, by controlling atotal light flux amount of light emitted from the light source 52R ofthe first light emitting optical system 51R, a total light flux amountof light emitted from the light source 52G of the second light emittingoptical system 51G, and a total light flux amount of light emitted fromthe light source 52B of the third light emitting optical system 51B. Forexample, it may be possible to perform switching, so as to emit warmwhite light or to emit blue white light, within the scope of the law.

Moreover, in the first embodiment, the first optical element 55 fsynthesizes the first light L_(R) and the second light L_(G) bytransmitting the first light L_(R) first light and reflecting the secondlight L_(G), and the second optical element 55 s synthesizes the firstlight L_(R), the second light L_(G), and the third light L_(B) bytransmitting the first light L_(R) and the second light L_(G)synthesized by the first optical element 55 f and reflecting the thirdlight L_(B). However, for example, it may have a configuration where thethird light L_(B) and the second light L_(G) are synthesized in thefirst optical element 55 f, and the third light L_(B) and the secondlight L_(G) synthesized by the first optical element 55 f and the firstlight L_(R) are synthesized in the second optical element 55 s. In thiscase, the positions of the first light emitting optical system 51R andthe third light emitting optical system 51B of the first embodiment areswitched. Moreover, in this case, it will have a configuration where thethird 0th-order light LC_(B) and the second 0th-order light LC_(G) aresynthesized in the first optical element 55 f, and the third 0th-orderlight LC_(B) and the second 0th-order light LC_(G) synthesized by thefirst optical element 55 f and the first 0th-order light LC_(R) aresynthesized in the second optical element 55 s. Moreover, in the firstembodiment, a band pass filter that transmits light of a predeterminedwavelength band and reflects light of other wavelength bands may be usedin the first optical element 55 f or the second optical element 55 s.The synthesis optical system 55 may combine and synthesize externalshapes of lights emitted from the respective light emitting opticalsystems, and is not limited to the first embodiment.

Moreover, in the first embodiment, the 0th-order lights LC_(R), LC_(G),and LC_(B) advancing and passing through the respective diffractiongratings 54R, 54G, and 54B are synthesized by the synthesis opticalsystem 55, and projected to the projection area AR. However, the0th-order lights LC_(R), LC_(G), and LC_(B) may not be synthesized bythe synthesis optical system 55, and may be projected to different areaswithin the range RNG that is a blind spot of a driver of an automobile.However, as described above, in the case where reducing pedestrians orthe like outside a vehicle from being unnecessarily aware of theprojection area AR, it is preferable that the 0th-order lights LC_(R),LC_(G), and LC_(B) advancing and passing through the respectivediffraction gratings 54R, 54G, and 54B are synthesized by the synthesisoptical system 55, and projected to the projection area AR.

In the first and second embodiments, a light distribution pattern of thelow beam L is formed as a light distribution pattern for dark placeillumination. However, it is not limited to a light distribution patternof the low beam L, if it is a light distribution pattern for dark placeillumination. Note that, a light distribution pattern for dark placeillumination is used at night or in dark places such as tunnels. Forexample, there are cases where a light distribution pattern of the lowbeam L, and a light distribution pattern of light for visuallyrecognizing a sign positioned outside, for example, above this lightdistribution pattern, are formed as a light distribution pattern fordark place illumination. In this case, it is preferable that light forvisually recognizing a sign is included in high order diffracted lightdiffracted by the respective diffraction gratings 54R, 54G, and 54B.Moreover, for example, a light distribution pattern of a high beam maybe formed as a light distribution pattern for dark place illumination.

Moreover, in the first and second embodiments, a headlight of anautomobile is exemplified as the vehicle headlight 1. However, the firstand second embodiments are not limited to a headlight of an automobile,and may be used as a headlight of another vehicle. The first and secondembodiments are not limited to a headlight, and may be a lamp such as arear light, a tail light, a brake light, or an indicator light.

That is, the present invention exemplified in the first and secondembodiments may be a vehicle illumination lamp such as follows. Namely,the vehicle illumination lamp includes a light source, and a diffractiongrating that diffracts light incident from the light source. The lightdiffracted by this diffraction grating is irradiated in a predeterminedlight distribution pattern, and a projection area to which are projectedcomponents advancing and passing through the diffraction grating amongthe light incident on the diffraction grating is positioned below thelight distribution pattern and within a range in which a field of viewof a driver of a vehicle is obstructed by the vehicle. It can be easilyoperated, if such a vehicle illumination lamp.

Third Embodiment

Next, a third embodiment of the present invention will be described.Note that, overlapping descriptions attached with the same referencenumerals, except for particular descriptions, will be omitted forconstituent elements the same or equivalent to those of the firstembodiment. FIG. 6 is a cross-sectional view schematically showing avehicle that includes a vehicle headlight according to the presentembodiment. As shown in FIG. 6 , the vehicle headlight 1 in the presentembodiment is different for the point that an optical element 60 isincluded.

The optical system unit 50 of the present embodiment includes a firstlight emitting optical system 51R, a second light emitting opticalsystem 51G, a third light emitting optical system 51B, a synthesisoptical system 55, a cover 59, and an optical element 60.

The optical element 60 is an optical element that lowers an energydensity of light. A light shielding element or a light diffusing elementcan be provided, for example, as the optical element 60. An example thatapplies a black anodization process to a metal plate such as aluminum,or an example that molds a substrate and a light shielding material suchas carbon black can be provided as a specific example of a lightshielding element. A lens, sheet or the like that diffuses or scatterslight can be provided as a specific example of a light diffusingelement.

Such an optical element 60 is disposed on an optical path of a 0th-orderlight beam LC between a projection area of the 0th-order light beam LCand diffraction gratings 54R, 54G, and 54B. The optical element 60 ofthe present embodiment is disposed within a housing 10. In the exampleshown in FIG. 6 , the optical element 60 is disposed on the surface of afront cover 12 on a lamp chamber R side, and the distance of an opticalpath between the optical element 60 and the diffraction grating 54Bclosest to the optical element 60 is set as, for example, 100 mm.

Next, the emission of light by the vehicle headlight 1 of the presentembodiment will be described.

Similar to the first embodiment, first, by supplying power from a powersource that is not illustrated, laser light is emitted from therespective light sources 52R, 52G, and 52B. As described above, redlaser light is emitted from the light source 52R, green laser light isemitted from the light source 52G, and blue laser light is emitted fromthe light source 52B. The respective laser lights are collimated bycollimator lenses 53R, 53G, and 53B, and afterwards are incident on thediffraction gratings 54R, 54G, and 54B. Then, as described above, therespective laser lights are diffracted by the diffraction gratings 54R,54G, and 54B, the first light L_(R) that is a red component of light ofa light distribution pattern of the low beam L is emitted from the firstlight emitting optical system 51R, the second light L_(G) that is agreen component of light of a light distribution pattern of the low beamL is emitted from the second light emitting optical system 51G, and thethird light L_(B) that is a blue component of light of a lightdistribution pattern of the low beam L is emitted from the third lightemitting optical system 51B. Moreover, as described above, the first0th-order light LC_(R) that is a red component of 0th-order light isemitted from the first light emitting optical system 51R, the second0th-order light LC_(G) that is a green component of 0th-order light isemitted from the second light emitting optical system 51G, and the third0th-order light LC_(B) that is a blue component of the 0th-order lightis emitted from the third light emitting optical system 51B, as0th-order lights advancing and passing through the diffraction gratings54R, 54G, and 54B.

In the synthesis optical system 55, first, the first light L_(R) and thesecond light L_(G) are synthesized and emitted by the first opticalelement 55 f, and the first 0th-order light LC_(R) and the second0th-order light LC_(G) are synthesized and emitted by the first opticalelement 55 f. The first light L_(R) and the second light L_(G)synthesized by the first optical element 55 f are synthesized with thethird light L_(B) by the second optical element 55 s, and the first0th-order light LC_(R) and the second 0th-order light LC_(G) synthesizedby the first optical element 55 f are synthesized with the third0th-order light LC_(B) by the second optical element 55 s. At this time,since the respective lights L_(R), L_(G), and L_(B) have an externalshape the same as the external shape of the low beam L, the externalshapes of the respective lights L_(R), L_(G), and L_(B) will besynthesized by matching each other. In addition, since the externalshapes of the respective 0th-order lights LC_(R), LC_(G), and LC_(B) arealso the same, the external shapes of the respective 0th-order lightsLC_(R), LC_(G), and LC_(B) will be synthesized by matching each other.Namely, the positions of each of the light emitting optical systems andthe synthesis optical system are finely adjusted, so that the externalshape of the first light L_(R), the external shape of the second lightL_(G), and the external shape of the third light L_(B), and also theexternal shape of the first 0th-order light LC_(R), the external shapeof the second 0th-order light LC_(G), and the external shape of thethird 0th-order light LC_(B), are combined by the synthesis opticalsystem such as described above.

In this way, light in which the red first light L_(R), the green secondlight L_(G), and the blue third light L_(B) are synthesized becomeswhite, and this white light is emitted from the synthesis optical system55 as the low beam L. Moreover, light in which the red first 0th-orderlight LC_(R), the green second 0th-order light LC_(G), and the bluethird 0th-order light LC_(B) are synthesized becomes white, and thiswhite light is emitted from the synthesis optical system 55 as the0th-order light beam LC.

The 0th-order light beam LC emitted from the synthesis optical system 55is emitted from the opening 59H of the cover 59, is irradiated on theoptical element 60 attached to the surface of the front cover 12 on thelamp chamber R side, and an energy density of the 0th-order light beamLC is lowered by this optical element 60.

The low beam L emitted from the synthesis optical system 55 is emittedfrom the opening 59H of the cover 59, emitted from the vehicle headlight1 to the front of the vehicle via the front cover 12, and irradiated ina predetermined light distribution pattern. In the present embodiment,irradiation is performed in the light distribution pattern PTN_(L) ofthe low beam L shown in FIG. 3 .

As described above, the vehicle headlight 1 of the present embodimentincludes the light sources 52R, 52G, and 52B, and the diffractiongratings 54R, 54G, and 54B that diffract lights incident from the lightsources 52R, 52G, and 52B. High order diffracted light diffracted by thediffraction gratings 54R, 54G, and 54B, among the lights emitted fromthe diffraction gratings 54R, 54G, 54B, is irradiated in the lightdistribution pattern PTN_(L) of the low beam L.

In addition to this, the vehicle headlight 1 of the present embodimentincludes the optical element 60. This optical element 60 is disposed onan optical path of the 0th-order light beam LC between the projectionarea of the 0th-order light beam LC and the diffraction gratings 54R,54G, and 54B, and lowers an energy density of the 0th-order light beamLC.

Therefore, in the vehicle headlight 1 of the present embodiment, even ifa light intensity of 0th-order light is higher than a light intensity ofhigh order diffracted light, among lights emitted from the diffractiongratings 54R, 54G, and 54B, an energy density of this 0th-order lightcan be lowered by the optical element 60. Accordingly, it is possible tosuppress the projection area of 0th-order light from becoming noticeablybrighter than the light distribution pattern PTN_(L) by high orderdiffracted light among lights emitted from the diffraction gratings 54R,54G, and 54B. In this way, the vehicle headlight 1 of the presentembodiment can be easily operated compared to the case where notincluding the optical element 60.

In the present embodiment, the optical element 60 is disposed within thehousing 10 such as described above. Accordingly, there will be areduction of 0th-order light being emitted outside the vehicle.Therefore, it is possible to suppress the projection area of the0th-order light beam LC from becoming noticeably bright outside thevehicle, and as a result of this, it is possible to suppress a driver,pedestrian or the like from being unnecessarily aware of the projectionarea.

Moreover, in the present embodiment, the optical element 60 may be alight shielding element or a light diffusing element such as describedabove. Accordingly, in the vehicle headlight 1 of the presentembodiment, a light shielding element or a light diffusing element canbe selected as the optical element 60, in accordance with the type orthe like of a vehicle mounted with the vehicle headlight 1.

Moreover, in the case of the present embodiment, the projection area ispositioned outside the light distribution pattern PTN_(L) of the lowbeam L. In this case, it is possible to suppress a part of the lightdistribution pattern PTN_(L) from becoming noticeably bright, comparedto the case where the projection area is positioned within the lightdistribution pattern PTN_(L) of the low beam L, and as a result of this,it can be easier to operate.

Moreover, the vehicle headlight 1 of the present embodiment has aplurality of light emitting optical systems including one light sourceand one diffraction grating. Namely, the vehicle headlight 1 has a firstlight emitting optical system 51R including one light source 52R and onediffraction grating 54R, a second light emitting optical system 51Gincluding one light source 52G and one diffraction grating 54G, and athird light emitting optical system 51B including one light source 52Band one diffraction grating 54B. In addition to this, the vehicleheadlight 1 of the present embodiment further includes a synthesisoptical system 55 that synthesizes lights emitted from the respectivelight emitting optical systems 51R, 51G, and 51B. Also, the respectivelight sources 52R, 52G, and 52B emit light of mutually differentpredetermined wavelengths, and the respective diffraction gratings 54R,54G, and 54B diffract light from the light sources 52R, 52G, and 52B sothat light synthesized by the synthesis optical system 55 has the lightdistribution pattern PTN_(L) of the low beam L.

In this case, light having a predetermined wavelength emitted from therespective light sources 52R, 52G, and 52B is diffracted by thediffraction gratings 54R, 54G, and 54B, and the light distributionpattern PTN_(L) is formed. At this time, in the respective lightemitting optical systems 51R, 51G, and 51B, since light diffracted bythe diffraction gratings 54R, 54G, and 54B has a predeterminedwavelength, it is possible to suppress color bleeding from occurringnear edges of the light distribution pattern PTN_(L) in the lightsemitted from the respective diffraction gratings 54R, 54G, and 54B, evenif the diffraction gratings 54R, 54G, and 54B have a wavelengthdependency. In this way, light having the light distribution patternPTN_(L) in which color bleeding is suppressed is synthesized by thesynthesis optical system 55, and a light distribution pattern PTN_(L) ofthe low beam L is formed. Therefore, the low beam L irradiated by thevehicle headlight 1 of the present embodiment can suppress colorbleeding from appearing near edges of the light distribution patternPTN_(L).

Moreover, in the vehicle headlight 1 of the present embodiment, the0th-order lights LC_(R), LC_(G), and LC_(B) advancing and passingthrough the respective diffraction gratings 54R, 54G, and 54B aresynthesized by the synthesis optical system 55, and the optical element60 lowers an energy density of the 0th-order light beam LC synthesizedby the synthesis optical system 55.

Accordingly, an irradiation area of 0th-order light irradiated on theoptical element 60 can be reduced, compared to the case where the0th-order lights advancing and passing through the respectivediffraction gratings 54R, 54G, and 54B are not synthesized. Therefore,it is possible to suppress a lowering by the optical element 60 of anenergy density of high order diffracted light among lights emitted fromthe diffraction gratings 54R, 54G, and 54B.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be described indetail with reference to FIG. 7 . Note that, overlapping descriptionsattached with the same reference numerals, except for particulardescriptions, will be omitted for constituent elements the same orequivalent to those of the third embodiment.

FIG. 7 is a figure showing, similar to FIG. 2 , an optical system unitof a vehicle headlight according to the present embodiment. As shown inFIG. 7 , the optical system unit 50 of the vehicle headlight of thepresent embodiment is different to the optical system unit 50 of thethird embodiment for the point of not including the synthesis opticalsystem 55, and emitting the respective lights emitted from the firstlight emitting optical system 51R, the second light emitting opticalsystem 51G, and the third light emitting optical system 51B from thecover 59, in a state where not synthesized. In the present embodiment,the first light emitting optical system 51R, the second light emittingoptical system 51G, and the third light emitting optical system 51B havean irradiation direction of light on an opening 59H side of the cover59.

In the present embodiment, similar to the third embodiment, in thediffraction grating 54R of the first light emitting optical system 51R,the diffraction grating 54G of the second light emitting optical system51G, and the diffraction grating 54B of the third light emitting opticalsystem 51B, respectively, light is emitted so that synthesized lightforms a light distribution pattern of the low beam L.

Namely, the first light L_(R) emitted from the diffraction grating 54R,the second light L_(G) emitted from the diffraction grating 54G, and thethird light L_(B) emitted from the diffraction grating 54B arerespectively emitted from the opening 59H of the cover 59, andirradiated to the outside of the vehicle headlight via the front cover12. At this time, the first light L_(R), the second light L_(G), and thethird light L_(B), and also the first 0th-order light LC_(R), the second0th-order light LC_(G), and the third 0th-order light LC_(B), areirradiated so that the external shapes of the respective lightdistribution patterns substantially match each other at a focal positionseparated a predetermined distance from the vehicle. This distance fromthe vehicle is, for example, 25 m. Namely, in the present embodiment,the irradiation directions of light of the first light emitting opticalsystem 51R, the second light emitting optical system 51G, and the thirdlight emitting optical system 51B are finely adjusted, so that theexternal shapes match each other such as described above.

Moreover, the optical system unit 50 of the vehicle headlight isdifferent to the optical system unit 50 of the third embodiment for thepoint of including, instead of the optical element 60, optical elements60A to 60C for lowering an energy density of 0th-order lights emittedfrom the first light emitting optical system 51R, the second lightemitting optical system 51G, and the third light emitting optical system51B. The optical element 60A is disposed on an optical path of the first0th-order light LC_(R) between the projection area of the first0th-order light LC_(R) and the diffraction grating 54R. The opticalelement 60B is disposed on an optical path of the second 0th-order lightLC_(G) between the projection area of the second 0th-order light LC_(G)and the diffraction grating 54G, and the optical element 60C is disposedon an optical path of the third 0th-order light LC_(B) between theprojection area of the third 0th-order light LC_(B) and the diffractiongrating 54B. While the arrangement positions of the optical elements 60Ato 60C are positions overlapping with the first light L_(R) emitted fromthe diffraction grating 54R, the second light L_(G) emitted from thediffraction grating 54G, and the third light L_(B) emitted from thediffraction grating 54B, they may be at positions that do not overlap.In the present embodiment, the optical elements 60A to 60C are disposedwithin the cover 59, and are fixed to the cover 59 via a fixture that isnot illustrated. The distance of an optical path between the respectiveoptical elements 60A to 60C and the diffraction grating 54R is, forexample, 100 mm. Therefore, it can be understood that the optical systemunit 50 of the present embodiment has a configuration that is largerthan that of the optical system unit 50 of the third embodiment.

According to the vehicle headlight of the present embodiment, since thesynthesis optical system 55 of the third embodiment is not used, it ispossible to form a simple configuration. Moreover, even if a lightintensity of 0th-order light is higher than a light intensity of highorder diffracted light, among lights emitted from the diffractiongratings 54R, 54G, and 54B, an energy density of this 0th-order lightcan be lowered by the optical elements 60A to 60C. Therefore, even ifthe synthesis optical system 55 is not used, similar to the thirdembodiment, it is possible to suppress the projection area of 0th-orderlight from becoming noticeably brighter than the light distributionpattern PTN_(L) by high order diffracted light.

In the third and fourth embodiments, the first light emitting opticalsystem that emits a red component of the first light L_(R), the secondlight emitting optical system that emits a green component of the secondlight L_(G), and the third light emitting optical system that emits ablue component of the third light L_(B), are included. However, in thethird and fourth embodiments, the lights emitted from the light sourcesrespectively included in the three light emitting optical systems arenot limited to red, green, and blue, as long as they have respectivelydifferent predetermined wavelengths.

Moreover, the number of light emitting optical systems may be one ortwo. In addition, the number of light emitting optical systems may bethree or more. In this case, a fourth light emitting optical system thatemits a yellow component of light of the low beam L may be provided. Forexample, in addition to the red, green, and blue light emitting opticalsystems, the fourth light emitting optical system may emit a yellowcomponent of light of the low beam L. Moreover, in the case where alight intensity of a part of red, green, and blue is low, the fourthlight emitting optical system may emit a color component of light thesame as the color with a low light intensity.

Moreover, in the third and fourth embodiments, a white balanceadjustment circuit may be further provided. This white balanceadjustment circuit can achieve a desired white balance, by controlling atotal light flux amount of light emitted from the light source 52R ofthe first light emitting optical system 51R, a total light flux amountof light emitted from the light source 52G of the second light emittingoptical system 51G, and a total light flux amount of light emitted fromthe light source 52B of the third light emitting optical system 51B. Forexample, it may be possible to perform switching, so as to emit warmwhite light, or to emit blue white light, within the scope of the law.

In the third embodiment, the first optical element 55 f synthesizes thefirst light L_(R) and the second light L_(G) by transmitting the firstlight L_(R) first light and reflecting the second light L_(G), and thesecond optical element 55 s synthesizes the first light L_(R), thesecond light L_(G), and the third light L_(B) by transmitting the firstlight L_(R) and the second light L_(G) synthesized by the first opticalelement 55 f and reflecting the third light L_(B). However, for example,it may have a configuration where the third light L_(B) and the secondlight L_(G) are synthesized in the first optical element 55 f, and thethird light L_(B) and the second light L_(G) synthesized by the firstoptical element 55 f and the first light L_(R) are synthesized in thesecond optical element 55 s. In this case, the positions of the firstlight emitting optical system 51R and the third light emitting opticalsystem 51B of the third embodiment are switched. Moreover, in this case,it will have a configuration where the third 0th-order light LC_(B) andthe second 0th-order light LC_(G) are synthesized in the first opticalelement 55 f, and the third 0th-order light LC_(B) and the second0th-order light LC_(G) synthesized by the first optical element 55 f andthe first 0th-order light LC_(R) are synthesized in the second opticalelement 55 s. In the third embodiment, a band pass filter that transmitslight of a predetermined wavelength band and reflects light of otherwavelength bands may be used in the first optical element 55 f or thesecond optical element 55 s. The synthesis optical system 55 may combineand synthesize external shapes of lights emitted from the respectivelight emitting optical systems, and is not limited to the thirdembodiment.

Moreover, in the third embodiment, the 0th-order lights LC_(R), LC_(G),and LC_(B) advancing and passing through the respective diffractiongratings 54R, 54G, and 54B may not be synthesized by the synthesisoptical system 55, and may be irradiated on different areas of theoptical element 60. However, as described above, in the case wherereducing an irradiation area of 0th-order light irradiated on theoptical element 60, and suppressing a lowering of an energy density ofhigh order diffracted light by the optical element 60, it is preferablethat the 0th-order lights LC_(R), LC_(G), and LC_(B) advancing andpassing through the respective diffraction gratings 54R, 54G, and 54Bare synthesized by the synthesis optical system 55.

In the third and fourth embodiments, while the projection area ispositioned outside of the light distribution pattern PTN_(L) of the lowbeam L, it may be positioned within this light distribution patternPTN_(L). In this case, it is preferable that the projection area isincluded within an area having a light intensity of half a value or lessof a highest light intensity from within a light intensity distributionof high order diffracted light diffracted by the diffraction gratings54R, 54G, and 54B, among the light distribution pattern PTN_(L) of thelow beam L. According to this, it will be easy for a light intensitydistribution of the light distribution pattern to be smoothly formed, onthe basis of a position having a highest light intensity within thelight intensity distribution, compared to the case where the projectionarea is included in an area higher than half a value of a highest lightintensity within the light intensity distribution of high orderdiffracted light.

Moreover, even though the optical element 60 of the third and fourthembodiments may make an energy density of the entering 0th-order lightto be zero, or may emit the 0th-order light with an energy densitysmaller than an energy density of the entering 0th-order light. However,as described above, in the case where the projection area is positionedwithin the light distribution pattern PTN_(L) of the low beam L, it ispreferable to adopt the optical element 60 that emits 0th-order lightwith an energy density smaller than an energy density of the entering0th-order light. In this way, while using 0th-order light as the lightdistribution pattern PTN_(L) of the low beam L, it is possible tosuppress the projection area of 0th-order light from becoming noticeablybright in the light distribution pattern PTN_(L).

In the third and fourth embodiments, the light distribution patternPTN_(L) of the low beam L is formed as a light distribution pattern fordark place illumination. However, it is not limited to a lightdistribution pattern PTN_(L) of the low beam L, if it is a lightdistribution pattern for dark place illumination. Note that, a lightdistribution pattern for dark place illumination is used at night or indark places such as tunnels. For example, as shown in FIG. 8 , there arecases where the light distribution pattern PTN_(L) of the low beam L,and a light distribution pattern PTN_(S) of light for visuallyrecognizing a sign positioned outside, for example, above this lightdistribution pattern PTN_(L), are formed as a light distribution patternfor dark place illumination. In this case, it is preferable that lightfor visually recognizing a sign is included in high order diffractedlight diffracted by the respective diffraction gratings 54R, 54G, and54B. Further, for example, as shown in FIG. 9 , there are cases where alight distribution pattern PTN_(H) of a high beam is formed as a lightdistribution pattern for dark place illumination. Among this lightdistribution pattern PTN_(H) of a high beam, an area HA1 is an areahaving the highest light intensity, and an area HA2 is an area having alight intensity lower than that of the area HA1. Namely, the respectivediffraction gratings 54R, 54G, and 54B diffract light so thatsynthesized light forms the light distribution pattern PTN_(H) thatincludes a light intensity distribution of a high beam.

Moreover, in the third and fourth embodiments, a headlight of anautomobile is exemplified as the vehicle headlight 1. However, the thirdand fourth embodiments are not limited to a headlight of an automobile,and may be a headlight of another vehicle. Moreover, the third andfourth embodiments are not limited to a headlight, and may be a lampsuch as a rear light, a tail light, a brake light, or an indicatorlight.

That is, the present invention exemplified in the third and fourthembodiments may be a vehicle illumination lamp such as follows. Namely,the vehicle illumination lamp includes a light source, a diffractiongrating for diffracting light incident from the light source, and anoptical element disposed, between a projection area of light componentsadvancing and passing through the diffraction grating and thediffraction grating, on an optical path of the light components, andlowering an energy density of light. Light diffracted by the diffractiongrating from among light emitted from the diffraction grating isirradiated in a predetermined light distribution pattern. It can beeasily operated, if such a vehicle illumination lamp.

Fifth Embodiment

Next, a fifth embodiment of the present invention will be described.Note that, overlapping descriptions attached with the same referencenumerals, except for particular descriptions, will be omitted forconstituent elements the same or equivalent to those of the firstembodiment. FIG. 10 is a cross-sectional view schematically showing avehicle that includes a vehicle headlight according to the presentembodiment. FIG. 11 is an enlarged view of an optical system unit of thevehicle headlight of FIG. 10 . As shown in FIGS. 10 and 11 , while theconfiguration of the vehicle headlight 1 in the present embodiment isthe same as the configuration of the vehicle headlight 1 in the firstembodiment, a light distribution pattern of light emitted by the vehicleheadlight 1 of the present embodiment is different to a lightdistribution pattern of light emitted by the vehicle headlight 1 of thefirst embodiment.

The diffraction grating 54R of the present embodiment diffracts laserlight incident from the collimator lens 53R so as to have apredetermined light distribution pattern. Specifically, the diffractiongrating 54R, in the synthesis optical system 55 described later,diffracts laser light incident from the collimator lens 53R so thatlights respectively emitted from the first light emitting optical system51R, the second light emitting optical system 51G, and the third lightemitting optical system 51B have a light distribution pattern of thediffracted light beam LD. A light intensity distribution is alsoincluded in this light distribution pattern. Accordingly, thediffraction grating 54R of the present embodiment diffracts laser lightincident from the collimator lens 53R, so as to have a light intensitydistribution based on a light intensity distribution of a lightdistribution pattern of the diffracted light beam LD, along with lightdiffracted by the diffraction grating 54R having a same external shapeas an external shape of a light distribution pattern of the diffractedlight beam LD.

This light diffracted by the diffraction grating 54R is high orderdiffracted light having an order of 1 or more, and in addition to thishigh order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54R without being diffracted is emittedfrom the diffraction grating 54R. In the present embodiment, 0th-orderlight is emitted from the diffraction grating 54R, so that a projectionarea of the 0th-order light beam LC emitted from the synthesis opticalsystem 55 described later is positioned within a light distributionpattern of the low beam L formed by the 0th-order light beam LC and thediffracted light beam LD.

In this way, a red component of high order diffracted light among thelow beam L, and a red component of 0th-order light among the 0th-orderlight beam LC are emitted from the first light emitting optical system51R. In the present embodiment, a red component of high order diffractedlight emitted from the first light emitting optical system 51R is set asfirst light LD_(R), and a red component of the 0th-order light is set asfirst 0th-order light LC_(R).

The diffraction grating 54G diffracts laser light incident from thecollimator lens 53G so as to have a predetermined light distributionpattern, and the diffraction grating 54B diffracts laser light incidentfrom the collimator lens 53B so as to have a predetermined lightdistribution pattern. Specifically, the diffraction gratings 54G and54B, in the synthesis optical system 55, respectively diffract laserlight incident from the collimator lenses 53G and 53B so that lightsrespectively emitted from the first light emitting optical system 51R,the second light emitting optical system 51G, and the third lightemitting optical system 51B have a light distribution pattern of thediffracted light beam LD. A light intensity distribution is alsoincluded in the light distribution pattern, such as described above.Accordingly, the diffraction gratings 54G and 54B of the presentembodiment respectively diffract laser light incident from thecollimator lenses 53G and 53B, so as to have a light intensitydistribution based on a light intensity distribution of a lightdistribution pattern of the diffracted light beam LD, along with laserlight respectively emitted from the diffraction gratings 54G and 54Bhaving a same external shape as an external shape of a lightdistribution pattern of the diffracted light beam LD.

The light diffracted by this diffraction grating 54G is high orderdiffracted light having an order of 1 or more, and in addition to thishigh order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54G without being diffracted is emittedfrom the diffraction grating 54G. In the present embodiment, 0th-orderlight is emitted from the diffraction grating 54G, so that a projectionarea of the 0th-order light beam LC emitted from the synthesis opticalsystem 55 described later is positioned within a light distributionpattern of the low beam L formed by the 0th-order light beam LC and thediffracted light beam LD.

Similarly, this light diffracted by the diffraction grating 54B is highorder diffracted light having an order of 1 or more, and in addition tothis high order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54B without being diffracted is emittedfrom the diffraction grating 54B. In the present embodiment, 0th-orderlight is emitted from the diffraction grating 54B, so that a projectionarea of the 0th-order light beam LC emitted from the synthesis opticalsystem 55 described later is positioned within a light distributionpattern of the low beam L formed by the 0th-order light beam LC and thediffracted light beam LD.

In this way, a green component of high order diffracted light among thelow beam L, and a green component of 0th-order light among the 0th-orderlight beam LC are emitted from the second light emitting optical system51G. Moreover, a blue component of high order diffracted light among thelow beam L, and a blue component of 0th-order light among the 0th-orderlight beam LC are emitted from the third light emitting optical system51B. In the present embodiment, a green component of high orderdiffracted light emitted from the second light emitting optical system51G is set as second light LD_(G), a green component of 0th-order lightis set as second 0th-order light LC_(G), a blue component of high orderdiffracted light emitted from the third light emitting optical system51B is set as third light LD_(B), and a blue component of 0th-orderlight is set as third 0th-order light LC_(B). Therefore, in the presentembodiment, the first light LD_(R) has a longest wavelength, and thewavelength becomes shorter in the order of the second light LD_(G) andthe third light LD_(B). Similarly, the first 0th-order light LC_(R) hasa longest wavelength, and the wavelength becomes shorter in the order ofthe second 0th-order light LC_(G) and the third 0th-order light LC_(B).

Note that, a light intensity distribution based on a light intensitydistribution of a light distribution pattern of the diffracted lightbeam LD means that the light intensities of the respective high orderdiffracted lights emitted from the diffraction gratings 54R, 54G, and54B are high, at a portion where a light intensity in a lightdistribution pattern of the diffracted light beam LD is high.

The synthesis optical system 55 includes a first optical element 55 fand a second optical element 55 s. The first optical element 55 f is anoptical element that synthesizes the first light LD_(R) emitted from thefirst light emitting optical system 51R and the second light LD_(G)emitted from the second light emitting optical system 51G. Moreover, thefirst optical element 55 f is also an optical element that synthesizesthe first 0th-order light LC_(R) emitted from the first light emittingoptical system 51R and the second 0th-order light LC_(G) emitted fromthe second light emitting optical system 51G. In the present embodiment,the first optical element 55 f synthesizes the first light LD_(R) andthe second light LD_(G) by transmitting the first light LD_(R) andreflecting the second light LD_(G), and synthesizes the first 0th-orderlight LC_(R) and the second 0th-order light LC_(G) by transmitting thefirst 0th-order light LC_(R) and reflecting the second 0th-order lightLC_(G).

The second optical element 55 s is an optical element that synthesizesthe first light LD_(R) and the second light LD_(G) synthesized by thefirst optical element 55 f and the third light LD_(B) emitted from thethird light emitting optical system 51B. Moreover, the second opticalelement 55 s is also an optical element that synthesizes the first0th-order light LC_(R) and the second 0th-order light LC_(G) synthesizedby the first optical element 55 f and the third 0th-order light LC_(B)emitted from the third light emitting optical system 51B. In the presentembodiment, the second optical element 55 s synthesizes the first lightLD_(R), the second light LD_(G), and the third light LD_(B) bytransmitting the first light LD_(R) and the second light LD_(G)synthesized by the first optical element 55 f and reflecting the thirdlight LD_(B). Moreover, the second optical element 55 s synthesizes thefirst 0th-order light LC_(R), the second 0th-order light LC_(G), and thethird 0th-order light LC_(B) by transmitting the first 0th-order lightLC_(R) and the second 0th-order light LC_(G) synthesized by the firstoptical element 55 f and reflecting the third 0th-order light LC_(B).

An optical filter, in which an oxide film is layered on a glasssubstrate, can be included as such a first optical element 55 f andsecond optical element 55 s. By controlling the type and thickness ofthis oxide film, it is possible to form a configuration that transmitslight having a wavelength longer than a predetermined wavelength, andreflects light having a wavelength shorter than this wavelength.

In this way, the diffracted light beam LD is emitted, by having thefirst light LD_(R), the second light LD_(G), and the third light LD_(B)synthesized, and the 0th-order light beam LC is emitted, by having thefirst 0th-order light LC_(R), the second 0th-order light LC_(G), and thethird 0th-order light LC_(B) synthesized, from the synthesis opticalsystem 55.

Next, the emission of light by the vehicle headlight 1 of the presentembodiment will be described.

First, by supplying power from a power source that is not illustrated,laser light is emitted from the respective light sources 52R, 52G, and52B. As described above, red laser light is emitted from the lightsource 52R, green laser light is emitted from the light source 52G, andblue laser light is emitted from the light source 52B. The respectivelaser lights are collimated by collimator lenses 53R, 53G, and 53B, andafterwards are incident on the diffraction gratings 54R, 54G, and 54B.Then, as described above, the respective laser lights are diffracted bythe diffraction gratings 54R, 54G, and 54B, the first light LD_(R) thatis a red component of the diffracted light beam LD is emitted from thefirst light emitting optical system 51R, the second light LD_(G) that isa green component of the diffracted light beam LD is emitted from thesecond light emitting optical system 51G, and the third light LD_(B)that is a blue component of the diffracted light beam LD is emitted fromthe third light emitting optical system 51B. Moreover, as describedabove, by respectively advancing and passing through the diffractiongratings 54R, 54G, and 54B, the first 0th-order light LC_(R) that is ared component of the 0th-order light beam LC is emitted from the firstlight emitting optical system 51R, the second 0th-order light LC_(G)that is a green component of the 0th-order light beam LC is emitted fromthe second light emitting optical system 51G, and the third 0th-orderlight LC_(B) that is a blue component of the 0th-order light beam LC isemitted from the third light emitting optical system 51B.

In the synthesis optical system 55, first, the first light LD_(R) andthe second light LD_(G) are synthesized and emitted by the first opticalelement 55 f, and the first 0th-order light LC_(R) and the second0th-order light LC_(G) are synthesized and emitted by the first opticalelement 55 f. The first light LD_(R) and the second light LD_(G)synthesized by the first optical element 55 f are synthesized with thethird light LD_(B) by the second optical element 55 s, and the first0th-order light LC_(R) and the second 0th-order light LC_(G) synthesizedby the first optical element 55 f are synthesized with the third0th-order light LC_(B) by the second optical element 55 s. At this time,since the external shapes of the respective lights LD_(R), LD_(G), andLD_(B) are the same as the external shape of the diffracted light beamLD, the external shapes of the respective lights LD_(R), LD_(G), andLD_(B) will be synthesized by matching each other. In addition, sincethe external shapes of the respective 0th-order lights LC_(R), LC_(G),and LC_(B) are also the same, the external shapes of the respective0th-order lights LC_(R), LC_(G), and LC_(B) will be synthesized bymatching each other. Namely, the positions of each of the light emittingoptical systems and the synthesis optical system are finely adjusted, sothat the external shape of the first light LD_(R), the external shape ofthe second light LD_(G), and the external shape of the third lightLD_(B), and also the external shape of the first 0th-order light LC_(R),the external shape of the second 0th-order light LC_(G), and theexternal shape of the third 0th-order light LC_(B), are combined by thesynthesis optical system such as described above.

In this way, light in which the red first light LD_(R), the green secondlight LD_(G), and the blue third light LD_(B) are synthesized becomeswhite, and this white light is emitted from the synthesis optical system55 as the diffracted light beam LD. Moreover, light in which the redfirst 0th-order light LC_(R), the green second 0th-order light LC_(G),and the blue third 0th-order light LC_(B) are synthesized becomes white,and this white light is emitted from the synthesis optical system 55 asthe 0th-order light beam LC.

The diffracted light beam LD and the 0th-order light beam LC emittedfrom the synthesis optical system 55 are emitted from the opening 59H ofthe cover 59, and are emitted from the vehicle headlight 1 to the frontof the vehicle via the front cover 12. A light distribution pattern ofthe low beam L is formed in front of the vehicle by the diffracted lightbeam LD and the 0th-order light beam LC.

FIG. 12 is a diagram showing a light distribution pattern of a low beamand a light intensity distribution of this light distribution pattern inthe present embodiment. As shown in FIG. 12 , the light distributionpattern PTN_(L) of the low beam L includes a first area LA1, a secondarea LA2, and a third area LA3, and the light intensity decreases in theorder of the first area LA1, the second area LA2, and the third areaLA3.

The first area LA1 is an area having a light intensity higher than afirst light intensity threshold within a light intensity distribution ofthe diffracted light beam LD that is high order diffracted light, and inthis first area LA1, a portion P is included that has a highest lightintensity L_(H) within a light intensity distribution of the diffractedlight beam LD. The second area LA2 is an area having a light intensityequal to or less than the first light intensity threshold and higherthan a second light intensity threshold set lower than the first lightintensity threshold within a light intensity distribution of thediffracted light beam LD, and the third area LA3 is an area equal to orless than the second light intensity threshold within the lightintensity distribution of the diffracted light beam LD. The first lightintensity threshold is, for example, half a value of the highest lightintensity L_(H) within the light intensity distribution of thediffracted light beam LD.

Among such a light distribution pattern PTN_(L) of the low beam L, aprojection area PAR of 0th order light on which is irradiated the0th-order light beam LC is positioned within the first area LA1, and isalso positioned within a hot zone HZ narrower than this first area LA1.However, the light projection area PAR of the 0th-order light ispositioned to avoid the portion P having the highest light intensityL_(H) within the light intensity distribution of the diffracted lightbeam LD. Note that, the light intensity of the projection area PAR is atotal value of the light intensity of the diffracted light beam LD and alight intensity of the 0th-order light beam LC. In the example shown inFIG. 12 , while the light intensity of the projection area PAR is higherthan the highest light intensity L_(H) within the light intensitydistribution of the diffracted light beam LD, it may be lower than thelight intensity L_(H). For example, the light intensity of theprojection area PAR can be made lower than the light intensity L_(H), byhaving the diffracted light beam LD unirradiated on the projection areaPAR.

As described above, the vehicle headlight 1 of the present embodimentincludes the light sources 52R, 52G, and 52B, and the diffractiongratings 54R, 54G, and 54B that diffract lights incident from the lightsources 52R, 52G, and 52B.

Lights diffracted by the diffraction gratings 54R, 54G, and 54B aresynthesized by the synthesis optical system 55, and are emitted from thesynthesis optical system 55 as a diffracted light beam LD. Further,lights advancing and passing through the diffraction gratings 54R, 54G,and 54B are synthesized by the synthesis optical system 55, and areemitted from the synthesis optical system 55 as a 0th-order light beamLC. A light distribution pattern of the low beam L is formed by thediffracted light beam LD and the 0th-order light beam LC. As shown inFIG. 12 , the projection area PAR of the 0th-order light beam LC withinthe light distribution pattern is positioned within an area having alight intensity higher than half a value of the highest light intensityL_(H) within the light intensity distribution of the diffracted lightbeam LD that is high order diffracted light.

Therefore, even if the 0th-order light having a light intensity higherthan a light intensity of high order diffracted light is irradiated onthe projection area PAR, it is possible to suppress the projection areaPAR from becoming noticeably bright within the light distributionpattern PTN_(L) of the low beam L. Therefore, the vehicle headlight 1 ofthe present embodiment can be easily operated, compared to the casewhere the projection area PAR is disposed outside an area having a lightintensity higher than half a value of a highest light intensity L_(H)within a light intensity distribution of the diffracted light beam LD.

Note that, in the present embodiment, the projection area PAR ispositioned to avoid the portion P having the highest light intensityL_(H) within the light intensity distribution of the diffracted lightbeam LD. Therefore, it is possible to suppress the portion P having thehighest light intensity L_(H) within the light distribution patternPTN_(L) of the diffracted light beam LD from becoming excessivelybright.

Moreover, by having the projection area PAR disposed within the hot zoneHZ, while using the 0th-order light beam LC as the light distributionpattern PTN_(L) of the low beam L, it is possible to suppress theprojection area PAR from becoming noticeably bright in the lightdistribution pattern PTN_(L).

Moreover, the vehicle headlight 1 of the present embodiment has aplurality of light emitting optical systems including one light sourceand one diffraction grating. Namely, the vehicle headlight 1 has a firstlight emitting optical system 51R including one light source 52R and onediffraction grating 54R, a second light emitting optical system 51Gincluding one light source 52G and one diffraction grating 54G, and athird light emitting optical system 51B including one light source 52Band one diffraction grating 54B. In addition to this, the vehicleheadlight 1 of the present embodiment further includes a synthesisoptical system 55 that synthesizes lights emitted from the respectivelight emitting optical systems 51R, 51G, and 51B. Also, the respectivelight source 52R, 52G, and 52B emit light of mutually differentpredetermined wavelengths, and the respective diffraction gratings 54R,54G, and 54B emit light from the light source 52R, 52G, and 52B so thatlight synthesized by the synthesis optical system 55 has the lightdistribution pattern PTN_(L) of the low beam L.

In this case, the light distribution pattern PTN_(L) is formed throughthe diffraction gratings 54R, 54G, and 54B by lights of predeterminedwavelengths emitted from the respective light sources 52R, 52G, and 52B.At this time, in the respective light emitting optical systems 51R, 51G,and 51B, since light diffracted by the diffraction gratings 54R, 54G,and 54B has a predetermined wavelength, it is possible to suppress colorbleeding from occurring near edges of the light distribution patternPTN_(L) in the lights emitted from the respective diffraction gratings54R, 54G, and 54B, even if the diffraction gratings 54R, 54G, and 54Bhave a wavelength dependency. In this way, light having the lightdistribution pattern PTN_(L) in which color bleeding is suppressed issynthesized by the synthesis optical system 55, and a light distributionpattern PTN_(L) of the low beam L is formed. Therefore, the low beam Lirradiated by the vehicle headlight 1 of the present embodiment cansuppress color bleeding from appearing near edges of the lightdistribution pattern PTN_(L).

Moreover, in the vehicle headlight 1 of the present embodiment, the0th-order lights LC_(R), LC_(G), and LC_(B) advancing and passingthrough the respective diffraction gratings 54R, 54G, and 54B aresynthesized by the synthesis optical system 55, and are irradiated onthe projection area PAR. In this case, even if the diffraction gratings54R, 54G, and 54B have a wavelength dependency such as described above,the 0th-order lights LC_(R), LC_(G), and LC_(B) passing through therespective diffraction gratings 54R, 54G, and 54B can be made a samewhite color. Therefore, in the vehicle headlight 1 of the presentembodiment, it is possible to reduce a driver from being unnecessarilyaware of the projection area PAR, and it becomes easier to operate.

Sixth Embodiment

Next, a sixth embodiment of the present invention will be described indetail with reference to FIG. 13 . Note that, overlapping descriptionsattached with the same reference numerals, except for particulardescriptions, will be omitted for constituent elements the same orequivalent to those of the fifth embodiment.

FIG. 13 is a figure showing, similar to FIG. 11 , an optical system unitof a vehicle headlight according to the present embodiment. As shown inFIG. 13 , the optical system unit 50 of the vehicle headlight of thepresent embodiment is different to the optical system unit 50 of thefifth embodiment for the point of not including the synthesis opticalsystem 55, and emitting the respective lights emitted from the firstlight emitting optical system 51R, the second light emitting opticalsystem 51G, and the third light emitting optical system 51B from thecover 59, in a state where not synthesized. In the present embodiment,the first light emitting optical system 51R, the second light emittingoptical system 51G, and the third light emitting optical system 51B havean irradiation direction of light on an opening 59H side of the cover59.

In the present embodiment, similar to the fifth embodiment, in thediffraction grating 54R of the first light emitting optical system 51R,the diffraction grating 54G of the second light emitting optical system51G, and the diffraction grating 54B of the third light emitting opticalsystem 51B, respectively, light is emitted so that synthesized lightforms a light distribution pattern of the low beam L.

Namely, the first light LD_(R) emitted from the diffraction grating 54R,the second light LD_(G) emitted from the diffraction grating 54G, andthe third light LD_(B) emitted from the diffraction grating 54B arerespectively emitted from the opening 59H of the cover 59, andirradiated to the outside of the vehicle headlight via the front cover12. Moreover, the first 0th-order light LC_(R) emitted from thediffraction grating 54R, the second 0th-order light LC_(G) emitted fromthe diffraction grating 54G, and the third 0th-order light LC_(B)emitted from the diffraction grating 54B are respectively emitted fromthe opening 59H of the cover 59, and irradiated to the outside of thevehicle headlight via the front cover 12. At this time, the first lightLD_(R), the second light LD_(G), and the third light LD_(B), and alsothe first 0th-order light LC_(R), the second 0th-order light LC_(G), andthe third 0th-order light LC_(B), are irradiated so that the externalshapes of the respective light distribution patterns substantially matcheach other at a focal position separated a predetermined distance fromthe vehicle. This distance from the vehicle is, for example, 25 m.Accordingly, the light distribution pattern of the low beam L is formedat a position separated a predetermined distance from the vehicle. Thislight distribution pattern is the light distribution pattern PTN_(L)shown in FIG. 12 , and has a same light intensity distribution as thelight intensity distribution shown in FIG. 12 . Accordingly, similar tothe fifth embodiment, the projection area PAR of 0th-order light withinthe light distribution pattern PTN_(L) is positioned within an areahaving a light intensity higher than half a value of the highest lightintensity L_(H) within the light intensity distribution of thediffracted light beam LD that is high order diffracted light.

According to the vehicle headlight of the present embodiment, since thesynthesis optical system 55 of the fifth embodiment is not used, it ispossible to form a simple configuration. Moreover, according to thevehicle headlight of the present embodiment, since the projection areaPAR of 0th-order light is positioned within an area having a lightintensity higher than half a value of the highest light intensity L_(H)within the light intensity distribution of the high order diffractedlight, similar to the fifth embodiment, it is possible to suppress theprojection area PAR from becoming noticeably bright. Note that, theexternal shape of the first light LD_(R), the external shape of thesecond light LD_(G), and the external shape of the third light LD_(B),and also the external shape of the first 0th-order light LC_(R), theexternal shape of the second 0th-order light LC_(G), and the externalshape of the third 0th-order light LC_(B), of the present embodimenttend to slightly deviate from each other except for at the focalposition. However, when compared with light obtained by having whitelight incident on one diffraction grating, it is possible to suppressthis deviation of the external shapes. Therefore, according to thepresent embodiment, a vehicle headlight can be realized that is capableof suppressing color bleeding while being reduced in size.

Note that, in the fifth and sixth embodiments, the first light emittingoptical system that emits a red component of the first light LD_(R), thesecond light emitting optical system that emits a green component of thesecond light LD_(G), and the third light emitting optical system thatemits a blue component of the third light LD_(B), are included. However,in the vehicle headlight of the fifth and sixth embodiments, the lightsemitted from the light sources respectively included in the three lightemitting optical systems are not limited to red, green, and blue, aslong as they have respectively different predetermined wavelengths.

Moreover, the number of light emitting optical systems may be one ortwo. In addition, the number of light emitting optical systems may bethree or more. In this case, for example, a fourth light emittingoptical system that emits a yellow component of light of the low beam Lmay be provided. In this case, in addition to the red, green, and bluelight emitting optical systems, the fourth light emitting optical systemmay emit a yellow component of light of the low beam L. Moreover, in thecase where a light intensity of a part of red, green, and blue is low,the fourth light emitting optical system may emit a color component oflight the same as the color with a low light intensity.

Moreover, in the fifth and sixth embodiments, a white balance adjustmentcircuit may be further provided. This white balance adjustment circuitcan achieve a desired white balance, by controlling a total light fluxamount of light emitted from the light source 52R of the first lightemitting optical system 51R, a total light flux amount of light emittedfrom the light source 52G of the second light emitting optical system51G, and a total light flux amount of light emitted from the lightsource 52B of the third light emitting optical system 51B. For example,it may be possible to perform switching, so as to emit warm white lightor to emit blue white light, within the scope of the law.

Moreover, in the fifth embodiment, the first optical element 55 fsynthesizes the first light LD_(R) and the second light LD_(G) bytransmitting the first light LD_(R) first light and reflecting thesecond light LD_(G), and the second optical element 55 s synthesizes thefirst light LD_(R), the second light LD_(G), and the third light LD_(B)by transmitting the first light LD_(R) and the second light LD_(G)synthesized by the first optical element 55 f and reflecting the thirdlight LD_(B). However, for example, it may have a configuration wherethe third light LD_(B) and the second light LD_(G) are synthesized inthe first optical element 55 f, and the third light LD_(B) and thesecond light LD_(G) synthesized by the first optical element 55 f andthe first light LD_(R) are synthesized in the second optical element 55s. In this case, the positions of the first light emitting opticalsystem 51R and the third light emitting optical system 51B of the fifthembodiment are switched. Moreover, in this case, it will have aconfiguration where the third 0th-order light LC_(B) and the second0th-order light LC_(G) are synthesized in the first optical element 55f, and the third 0th-order light LC_(B) and the second 0th-order lightLC_(G) synthesized by the first optical element 55 f and the first0th-order light LC_(R) are synthesized in the second optical element 55s. In the fifth embodiment, a band pass filter that transmits light of apredetermined wavelength band and reflects light of other wavelengthbands may be used in the first optical element 55 f or the secondoptical element 55 s. The synthesis optical system 55 may combine andsynthesize external shapes of lights emitted from the respective lightemitting optical systems, and is not limited to the fifth embodiment.

Moreover, in the fifth embodiment, the 0th-order lights LC_(R), LC_(G),and LC_(B) advancing and passing through the respective diffractiongratings 54R, 54G, and 54B may not be synthesized by the synthesisoptical system 55, and may be irradiated on different areas of theprojection area PAR. However, as described above, in order to reduce adriver or the like from being unnecessarily aware of the projection areaPAR, it is preferable that the 0th-order lights LC_(R), LC_(G), andLC_(B) advancing and passing through the respective diffraction gratings54R, 54G, 54B are synthesized.

Moreover, in the fifth and sixth embodiments, while the projection areaPAR is positioned to avoid a position having the highest light intensityL_(H) within the light intensity distribution of high order diffractedlight, it may include this position. In this case, the brightest areawithin the light distribution pattern PTN_(L) of the low beam L will bemostly unchanged, regardless of whether or not the light intensity ofthe 0th-order light is large. Accordingly, it will be easy for the lightintensity distribution of the light distribution pattern PTN_(L) of thelow beam L to be more smoothly formed, on the basis of a position havinga highest light intensity within the light intensity distribution of thediffracted light beam LD. However, in order to suppress the portion Phaving the highest light intensity L_(H) within the light distributionpattern PTN_(L) of the diffracted light beam LD from becomingexcessively bright, it is preferable to be positioned to avoid theposition having the highest light intensity L_(H) within the lightintensity distribution of the diffracted light beam LD.

In the fifth and sixth embodiments, the light distribution patternPTN_(L) of the low beam L is formed as a light distribution pattern fordark place illumination. However, it is not limited to a lightdistribution pattern PTN_(L) of the low beam L, if it is a lightdistribution pattern for dark place illumination. Note that, a lightdistribution pattern for dark place illumination is used at night or indark places such as tunnels. For example, as shown in FIG. 14 , thereare cases where the light distribution pattern PTN_(L) of the low beamL, and a light distribution pattern PTN_(S) of light for visuallyrecognizing a sign positioned outside, for example, above this lightdistribution pattern PTN_(L), are formed as a light distribution patternfor dark place illumination. In this case, it is preferable that lightfor visually recognizing a sign is included in high order diffractedlight diffracted by the respective diffraction gratings 54R, 54G, and54B. Moreover, for example, a light distribution pattern of a high beammay be formed as a light distribution pattern for dark placeillumination.

Moreover, in the fifth and sixth embodiments, a headlight of anautomobile is exemplified as the vehicle headlight 1. However, the fifthand sixth embodiments are not limited to a headlight of an automobile,and may be a headlight of another vehicle. Further, the fifth and sixthembodiments are not limited to a headlight, and may be a lamp such as arear light, a tail light, a brake light, or an indicator light.

That is, the present invention exemplified in the fifth and sixthembodiments may be a vehicle illumination lamp such as follows. Namely,the vehicle illumination lamp includes a light source, and a diffractiongrating that diffracts light incident from the light source. A lightdistribution pattern having a predetermined light intensity distributionis formed by light diffracted by the diffraction grating and lightadvancing and passing through the diffraction grating. A projection areaof the light advancing and passing through the diffraction gratingwithin this light distribution pattern is positioned within an areahaving a light intensity higher than half a value of a highest lightintensity within a light intensity distribution of the light diffractedby the diffraction grating. It can be easily operated, if such a vehicleillumination lamp.

Seventh Embodiment

Next, a seventh embodiment of the present invention will be described.Note that, overlapping descriptions attached with the same referencenumerals, except for particular descriptions, will be omitted forconstituent elements the same or equivalent to those of the fifthembodiment. While the configuration of the vehicle headlight 1 in thepresent embodiment is the same as the configuration of the vehicleheadlight 1 in the fifth embodiment, a light distribution pattern oflight emitted by the vehicle headlight 1 of the present embodiment isdifferent to a light distribution pattern of light emitted by thevehicle headlight 1 of the fifth embodiment.

The diffraction grating 54R of the present embodiment emits the laserlight incident from the collimator lens 53R so as to have apredetermined light distribution pattern. Specifically, the diffractiongrating 54R, in the synthesis optical system 55, emits laser lightincident from the collimator lens 53R so that lights respectivelyemitted from the first light emitting optical system 51R, the secondlight emitting optical system 51G, and the third light emitting opticalsystem 51B have a light distribution pattern of the diffracted lightbeam LD. A light intensity distribution is also included in this lightdistribution pattern. Accordingly, the diffraction grating 54R of thepresent embodiment emits laser light incident from the collimator lens53R, so as to have a light intensity distribution based on a lightintensity distribution of a light distribution pattern of the diffractedlight beam LD, along with light diffracted by the diffraction grating54R having a same external shape as an external shape of a lightdistribution pattern of the diffracted light beam LD.

This light diffracted by the diffraction grating 54R is high orderdiffracted light having an order of 1 or more, and in addition to thishigh order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54R without being diffracted is emittedfrom the diffraction grating 54R. In the present embodiment, 0th-orderlight is emitted from the diffraction grating 54R, so that theprojection area of the 0th-order light beam LC emitted from thesynthesis optical system 55 is positioned within a light distributionpattern of the low beam L formed by the 0th-order light beam LC and thediffracted light beam LD. The diffraction grating 54R of the presentembodiment emits laser light incident from the collimator lens 53R, sothat high order diffracted light diffracted by the diffraction grating54R is unirradiated in the projection area of the 0th-order light beamLC. Therefore, in the projection area of the 0th-order light beam LC inthe light distribution pattern of the low beam L, the light intensity ofhigh order diffracted light diffracted by the diffraction grating 54R iszero.

In this way, a red component of high order diffracted light among thelow beam L, and a red component of 0th-order light among the 0th-orderlight beam LC are emitted from the first light emitting optical system51R. In the present embodiment, a red component of high order diffractedlight emitted from the first light emitting optical system 51R is set asfirst light LD_(R), and a red component of the 0th-order light is set asfirst 0th-order light LC_(R).

The diffraction grating 54G emits laser light incident from thecollimator lens 53G so as to have a predetermined light distributionpattern, and the diffraction grating 54B emits laser light incident fromthe collimator lens 53B so as to have a predetermined light distributionpattern. Specifically, the diffraction gratings 54G and 54B, in thesynthesis optical system 55, respectively diffract laser light incidentfrom the collimator lenses 53G and 53B so that lights respectivelyemitted from the first light emitting optical system 51R, the secondlight emitting optical system 51G, and the third light emitting opticalsystem 51B have a light distribution pattern of the diffracted lightbeam LD. A light intensity distribution is also included in the lightdistribution pattern, such as described above. Accordingly, thediffraction gratings 54G and 54B of the present embodiment respectivelydiffract laser light incident from the collimator lenses 53G and 53B, soas to have a light intensity distribution based on a light intensitydistribution of a light distribution pattern of the diffracted lightbeam LD, along with laser light respectively emitted from thediffraction gratings 54G and 54B having a same external shape as anexternal shape of a light distribution pattern of the diffracted lightbeam LD.

The light diffracted by this diffraction grating 54G is high orderdiffracted light having an order of 1 or more, and in addition to thishigh order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54G without being diffracted is emittedfrom the diffraction grating 54G. In the present embodiment, 0th-orderlight is emitted from the diffraction grating 54G, so that theprojection area of the 0th-order light beam LC emitted from thesynthesis optical system 55 is positioned within a light distributionpattern of the low beam L formed by the 0th-order light beam LC and thediffracted light beam LD. The diffraction grating 54G of the presentembodiment emits laser light entering from the collimator lens 53G sothat high order diffracted light diffracted by the diffraction grating54G is unirradiated in the projection area of the 0th-order light beamLC. Therefore, in the projection area of the 0th-order light beam LC inthe light distribution pattern of the low beam L, the light intensity ofhigh order diffracted light diffracted by the diffraction grating 54G iszero.

Similarly, this light diffracted by the diffraction grating 54B is highorder diffracted light having an order of 1 or more, and in addition tothis high order diffracted light, 0th-order light advancing and passingthrough the diffraction grating 54B without being diffracted is emittedfrom the diffraction grating 54B. In the present embodiment, 0th-orderlight is emitted from the diffraction grating 54B, so that theprojection area of the 0th-order light beam LC emitted from thesynthesis optical system 55 is positioned within the light distributionpattern of the low beam L formed by the 0th-order light beam LC and thediffracted light beam LD. The diffraction grating 54B of the presentembodiment emits laser light entering from the collimator lens 53B sothat high order diffracted light diffracted by the diffraction grating54B is unirradiated in the projection area of the 0th-order light beamLC. Therefore, in the projection area of the 0th-order light beam LC inthe light distribution pattern of the low beam L, the light intensity ofhigh order diffracted light diffracted by the diffraction grating 54B iszero.

In this way, a green component of high order diffracted light among thelow beam L, and a green component of 0th-order light among the 0th-orderlight beam LC are emitted from the second light emitting optical system51G. Moreover, a blue component of high order diffracted light among thelow beam L, and a blue component of 0th-order light among the 0th-orderlight beam LC are emitted from the third light emitting optical system51B. In the present embodiment, a green component of high orderdiffracted light emitted from the second light emitting optical system51G is set as second light LD_(G), a green component of 0th-order lightis set as second 0th-order light LC_(G), a blue component of high orderdiffracted light emitted from the third light emitting optical system51B is set as third light LD_(B), and a blue component of 0th-orderlight is set as third 0th-order light LC_(B). Therefore, in the presentembodiment, the first light LD_(R) has a longest wavelength, and thewavelength becomes shorter in the order of the second light LD_(G) andthe third light LD_(B). Similarly, the first 0th-order light LC_(R) hasa longest wavelength, and the wavelength becomes shorter in the order ofthe second 0th-order light LC_(G) and the third 0th-order light LC_(B).

Next, the emission of light by the vehicle headlight 1 of the presentembodiment will be described.

First, by supplying power from a power source that is not illustrated,laser light is emitted from the respective light sources 52R, 52G, and52B. As described above, red laser light is emitted from the lightsource 52R, green laser light is emitted from the light source 52G, andblue laser light is emitted from the light source 52B. The respectivelaser lights are collimated by collimator lenses 53R, 53G, and 53B, andafterwards are incident on the diffraction gratings 54R, 54G, and 54B.Then, as described above, the respective laser lights are diffracted bythe diffraction gratings 54R, 54G, and 54B, the first light LD_(R) thatis a red component of the diffracted light beam LD is emitted from thefirst light emitting optical system 51R, the second light LD_(G) that isa green component of the diffracted light beam LD is emitted from thesecond light emitting optical system 51G, and the third light LD_(B)that is a blue component of the diffracted light beam LD is emitted fromthe third light emitting optical system 51B. Moreover, as describedabove, by respectively advancing and passing through the diffractiongratings 54R, 54G, and 54B, the first 0th-order light LC_(R) that is ared component of the 0th-order light beam LC is emitted from the firstlight emitting optical system 51R, the second 0th-order light LC_(G)that is a green component of the 0th-order light beam LC is emitted fromthe second light emitting optical system 51G, and the third 0th-orderlight LC_(B) that is a blue component of the 0th-order light beam LC isemitted from the third light emitting optical system 51B.

In the synthesis optical system 55, first, the first light LD_(R) andthe second light LD_(G) are synthesized and emitted by the first opticalelement 55 f, and the first 0th-order light LC_(R) and the second0th-order light LC_(G) are synthesized and emitted by the first opticalelement 55 f. The first light LD_(R) and the second light LD_(G)synthesized by the first optical element 55 f are synthesized with thethird light LD_(B) by the second optical element 55 s, and the first0th-order light LC_(R) and the second 0th-order light LC_(G) synthesizedby the first optical element 55 f are synthesized with the third0th-order light LC_(B) by the second optical element 55 s. At this time,since the external shapes of the respective lights LD_(R), LD_(G), andLD_(B) are the same as the external shape of the diffracted light beamLD, the external shapes of the respective lights LD_(R), LD_(G), andLD_(B) will be synthesized by matching each other. In addition, sincethe external shapes of the respective 0th-order lights LC_(R), LC_(G),and LC_(B) are also the same, the external shapes of the respective0th-order lights LC_(R), LC_(G), and LC_(B) will be synthesized bymatching each other. Namely, the positions of each of the light emittingoptical systems and the synthesis optical system are finely adjusted, sothat the external shape of the first light LD_(R), the external shape ofthe second light LD_(G), and the external shape of the third lightLD_(B), and also the external shape of the first 0th-order light LC_(R),the external shape of the second 0th-order light LC_(G), and theexternal shape of the third 0th-order light LC_(B), are combined by thesynthesis optical system such as described above.

In this way, light in which the red first light LD_(R), the green secondlight LD_(G), and the blue third light LD_(B) are synthesized becomeswhite, and this white light is emitted from the synthesis optical system55 as the diffracted light beam LD. Moreover, light in which the redfirst 0th-order light LC_(R), the green second 0th-order light LC_(G),and the blue third 0th-order light LC_(B) are synthesized becomes white,and this white light is emitted from the synthesis optical system 55 asthe 0th-order light beam LC.

The diffracted light beam LD and the 0th-order light beam LC emittedfrom the synthesis optical system 55 are emitted from the opening 59H ofthe cover 59, and are emitted from the vehicle headlight 1 to the frontof the vehicle via the front cover 12. A light distribution pattern ofthe low beam L is formed in front of the vehicle by the diffracted lightbeam LD and the 0th-order light beam LC.

FIG. 15 is a figure showing a light distribution pattern of a low beam,and a light intensity distribution of this light distribution pattern,of the present embodiment. As shown in FIG. 15 , the light distributionpattern PTN_(L) of the low beam L includes a first area LA1, a secondarea LA2, and a third area LA3, and the light intensity decreases in theorder of the first area LA1, the second area LA2, and the third areaLA3.

The first area LA1 is an area having a light intensity higher than afirst light intensity threshold within a light intensity distribution ofthe diffracted light beam LD that is high order diffracted light, and inthis first area LA1, a portion P is included that has a highest lightintensity L_(H) within a light intensity distribution of the diffractedlight beam LD. The second area LA2 is an area having a light intensityequal to or less than the first light intensity threshold and higherthan a second light intensity threshold set lower than the first lightintensity threshold within a light intensity distribution of thediffracted light beam LD, and the third area LA3 is an area equal to orless than the second light intensity threshold within the lightintensity distribution of the diffracted light beam LD. The first lightintensity threshold is, for example, half a value of the highest lightintensity L_(H) within the light intensity distribution of thediffracted light beam LD.

Among such a light distribution pattern PTN_(L) of the low beam L, aprojection area PAR of 0th-order light on which is irradiated the0th-order light beam LC is included within the second area LA2, andoverlaps with a part of the first area LA1. Moreover, the lightintensity of the projection area PAR of 0th-order light is made lowerthan a highest light intensity L_(H) within the light intensitydistribution of the diffracted light beam LD.

FIG. 16 is a figure showing a light distribution pattern of a low beam Lof the case where the 0th-order light beam LC is unirradiated, and alight intensity distribution of this light distribution pattern. In thepresent embodiment such as described above, since the light intensity ofhigh order diffracted light irradiated on the projection area PAR of0th-order light is zero, in the case where the 0th-order light beam LCis unirradiated, such as shown in FIG. 16 , the projection area PAR ofthe 0th-order light in the light distribution pattern PTN_(L) of the lowbeam L will become a dark hole. By having the 0th-order light beam LCirradiated on the projection area PAR, the light distribution patternPTN_(L) of the low beam L shown in FIG. 15 is formed. Namely, while thelight intensity of the projection area PAR is a total value of the lightintensity of the diffracted light beam LD and the light intensity of the0th-order light beam LC, in the present embodiment, since a lightintensity of high order diffracted light irradiated on the projectionarea PAR is set as zero such as described above, the light intensity ofthe projection area PAR will match with the light intensity of the0th-order light beam LC.

As described above, the vehicle headlight 1 of the present embodimentincludes the light sources 52R, 52G, and 52B, and the diffractiongratings 54R, 54G, and 54B that diffract lights incident from the lightsources 52R, 52G, and 52B.

Lights emitted from the diffraction gratings 54R, 54G, and 54B aresynthesized by the synthesis optical system 55, and emitted from thesynthesis optical system 55 as a diffracted light beam LD and a0th-order light beam LC. A low beam L is obtained by the diffractedlight beam LD and the 0th-order light beam LC, and the low beam L isirradiated in a light distribution pattern PTN_(L) having apredetermined light intensity distribution. In the projection area PARof 0th-order light in the light distribution pattern PTN_(L), thediffracted light beam LD is unirradiated. As described above, thediffracted light beam LD is high order diffracted light diffracted bythe diffraction gratings 54R, 54G, and 54B.

Therefore, a light intensity of high order diffracted light in theprojection area PAR is smaller than a light intensity of lightirradiated on an outside peripheral edge of the projection area PAR.Accordingly, it is possible to suppress the projection area PAR beingnoticeably bright within the light distribution pattern PTN_(L) of thelow beam L, even if 0th-order light having a high light intensitycompared to a light intensity of high order diffracted light isirradiated on the projection area PAR. Therefore, the vehicle headlight1 of the present embodiment can be operated more easily, compared to thecase where a light intensity of high order diffracted light in theprojection area PAR is equal to or more than a light intensity of lightirradiated on an outside peripheral edge of the projection area PAR.

Note that, in the present embodiment, since the diffracted light beam LDis unirradiated on the projection area PAR such as described above, thelight intensity of high order diffracted light irradiated on thisprojection area PAR will be zero. Therefore, in the present embodiment,even in the case where a difference between the light intensity of0th-order light and the light intensity of high order diffracted lightis large, it will be easy to suppress the projection area PAR beingnoticeably bright within the light distribution pattern PTN_(L) of thelow beam L, and to form a smooth light intensity distribution as thewhole light distribution pattern PTN_(L).

As described above, since the light intensity of high order diffractedlight irradiated on the projection area PAR is set as zero, the lightintensity of the projection area PAR will become the light intensity of0th-order light. This light intensity of 0th-order light, such as shownin FIG. 15 , is lower than the highest light intensity L_(H) within thelight intensity distribution of the diffracted light beam LD that ishigh order diffracted light. Therefore, in the present embodiment, itwill be easy for the light intensity distribution of the lightdistribution pattern PTN_(L) to be smoothly formed, on the basis of theportion P having the highest light intensity L_(H) within the lightintensity distribution of the high order diffracted light.

In addition, in the case of the present embodiment, the lightdistribution pattern PTN_(L) of the low beam L includes a first areaLA1, a second area LA2 having a light intensity lower than a lightintensity of the first area LA1, and a third area LA3 having a lightintensity lower than a light intensity of the second area LA2. Theprojection area PAR is included within the second area LA2, and a partof the projection area PAR overlaps with the first area LA1. Therefore,it is possible to suppress the projection area PAR being noticeablybright within the light distribution pattern PTN_(L) of the low beam L,compared to the case where the projection area PAR is included in thethird area LA3, which is an area with a lowest light intensity withinthe light distribution pattern PTN_(L) of the low beam L.

Moreover, the vehicle headlight 1 of the present embodiment has aplurality of light emitting optical systems including one light sourceand one diffraction grating. Namely, the vehicle headlight 1 has a firstlight emitting optical system 51R including one light source 52R and onediffraction grating 54R, a second light emitting optical system 51Gincluding one light source 52G and one diffraction grating 54G, and athird light emitting optical system 51B including one light source 52Band one diffraction grating 54B. In addition to this, the vehicleheadlight 1 of the present embodiment further includes a synthesisoptical system 55 that synthesizes lights emitted from the respectivelight emitting optical systems 51R, 51G, and 51B. Also, the respectivelight sources 52R, 52G, and 52B emit light of mutually differentpredetermined wavelengths, and the respective diffraction gratings 54R,54G, and 54B emit light from the light sources 52R, 52G, and 52B so thatlight synthesized by the synthesis optical system 55 has the lightdistribution pattern of the low beam L.

In this case, lights of predetermined wavelengths emitted from therespective light sources 52R, 52G, and 52B are diffracted by thediffraction gratings 54R, 54G, and 54B, and a light distribution patternis formed. At this time, in the respective light emitting opticalsystems 51R, 51G, and 51B, since light diffracted by the diffractiongratings 54R, 54G, and 54B has a predetermined wavelength, it ispossible to suppress color bleeding from occurring near edges of a lightdistribution pattern in the lights emitted from the respectivediffraction gratings 54R, 54G, and 54B, even if the diffraction gratings54R, 54G, and 54B have a wavelength dependency. In this way, lighthaving a light distribution pattern in which color bleeding issuppressed is synthesized by the synthesis optical system 55, and thelight distribution pattern of the low beam L is formed. Therefore, thelow beam L irradiated by the vehicle headlight 1 of the presentembodiment can suppress color bleeding from appearing near edges of alight distribution pattern.

Moreover, in the vehicle headlight 1 of the present embodiment, the0th-order lights LC_(R), LC_(G), and LC_(B) advancing and passingthrough the respective diffraction gratings 54R, 54G, and 54B aresynthesized by the synthesis optical system 55, and are irradiated onthe projection area PAR. In this case, even if the diffraction gratings54R, 54G, and 54B have a wavelength dependency such as described above,the 0th-order lights LC_(R), LC_(G), and LC_(B) passing through therespective diffraction gratings 54R, 54G, and 54B can be made a samewhite color. Therefore, in the vehicle headlight 1 of the presentembodiment, it is possible to reduce a driver from being unnecessarilyaware of the projection area PAR, and it becomes easier to operate.

Eighth Embodiment

Next, an eighth embodiment of the present invention will be described.Note that, overlapping descriptions attached with the same referencenumerals, except for particular descriptions, will be omitted forconstituent elements the same or equivalent to those of the seventhembodiment.

Since the figure showing an optical system unit of a vehicle headlightaccording to the present embodiment is described similar to that of FIG.13 , the present embodiment will be described with reference to FIG. 13. As shown in FIG. 13 , the optical system unit 50 of the vehicleheadlight of the present embodiment is different to the optical systemunit 50 of the seventh embodiment for the point of not including thesynthesis optical system 55, and emitting the respective lights emittedfrom the first light emitting optical system 51R, the second lightemitting optical system 51G, and the third light emitting optical system51B from the cover 59, in a state where not synthesized. In the presentembodiment, the first light emitting optical system 51R, the secondlight emitting optical system 51G, and the third light emitting opticalsystem 51B have an irradiation direction of light on an opening 59H sideof the cover 59.

In the present embodiment, similar to the seventh embodiment, in thediffraction grating 54R of the first light emitting optical system 51R,the diffraction grating 54G of the second light emitting optical system51G, and the diffraction grating 54B of the third light emitting opticalsystem 51B, respectively, light is emitted so that synthesized lightforms a light distribution pattern of the low beam L.

Namely, the first light LD_(R) emitted from the diffraction grating 54R,the second light LD_(G) emitted from the diffraction grating 54G, andthe third light LD_(B) emitted from the diffraction grating 54B arerespectively emitted from the opening 59H of the cover 59, andirradiated to the outside of the vehicle headlight via the front cover12. Moreover, the first 0th-order light LC_(R) emitted from thediffraction grating 54R, the second 0th-order light LC_(G) emitted fromthe diffraction grating 54G, and the third 0th-order light LC_(B)emitted from the diffraction grating 54B are respectively emitted fromthe opening 59H of the cover 59, and irradiated to the outside of thevehicle headlight via the front cover 12. At this time, the first lightLD_(R), the second light LD_(G), and the third light LD_(B), and alsothe first 0th-order light LC_(R), the second 0th-order light LC_(G), andthe third 0th-order light LC_(B), are irradiated so that the externalshapes of the respective light distribution patterns substantially matcheach other at a focal position separated a predetermined distance fromthe vehicle. This distance from the vehicle is, for example, 25 m.Accordingly, the light distribution pattern of the low beam L is formedat a position separated a predetermined distance from the vehicle. Thislight distribution pattern is the light distribution pattern PTN_(L)shown in FIG. 15 , and has a same light intensity distribution as thelight intensity distribution shown in FIG. 15 . Accordingly, similar tothe seventh embodiment, the diffracted light beam LD is unirradiated inthe projection area PAR of 0th-order light, and a light intensity ofhigh order diffracted light in the projection area PAR is smaller than alight intensity of light irradiated on an outside peripheral edge of theprojection area PAR.

According to the vehicle headlight of the present embodiment, since thesynthesis optical system 55 of the seventh embodiment is not used, it ispossible to form a simple configuration. Moreover, according to thevehicle headlight of the present embodiment, since a light intensity ofhigh order diffracted light in the projection area PAR is smaller than alight intensity of light irradiated on an outside peripheral edge of theprojection area PAR, similar to the seventh embodiment, it is possibleto suppress the projection area PAR being noticeably bright within thelight distribution pattern PTN_(L). Note that, the external shape of thefirst light LD_(R), the external shape of the second light LD_(G), andthe external shape of the third light LD_(B), and also the externalshape of the first 0th-order light LC_(R), the external shape of thesecond 0th-order light LC_(G), and the external shape of the third0th-order light LC_(B), of the present embodiment tend to slightlydeviate from each other except for at the focal position. However, whencompared with light obtained by having white light incident on onediffraction grating, it is possible to suppress this deviation of theexternal shapes. Therefore, according to the present embodiment, avehicle headlight can be realized that is capable of suppressing colorbleeding while being reduced in size.

Note that, in the seventh and eighth embodiments, the first lightemitting optical system that emits a red component of the first lightLD_(R), the second light emitting optical system that emits a greencomponent of the second light LD_(G), and the third light emittingoptical system that emits a blue component of the third light LD_(B),are included. However, in the vehicle headlight of the seventh andeighth embodiments, the lights emitted from the light sourcesrespectively included in the three light emitting optical systems arenot limited to red, green, and blue, as long as they have respectivelydifferent predetermined wavelengths.

Moreover, the number of light emitting optical systems may be one ortwo. In addition, the number of light emitting optical systems may bethree or more. In this case, for example, a fourth light emittingoptical system that emits a yellow component of light of the low beam Lmay be provided. In this case, in addition to the red, green, and bluelight emitting optical systems, the fourth light emitting optical systemmay emit a yellow component of light of the low beam L. Moreover, in thecase where a light intensity of a part of red, green, and blue is low,the fourth light emitting optical system may emit a color component oflight the same as the color with a low light intensity.

Moreover, in the seventh and eighth embodiments, a white balanceadjustment circuit may be further provided. This white balanceadjustment circuit can achieve a desired white balance, by controlling atotal light flux amount of light emitted from the light source 52R ofthe first light emitting optical system 51R, a total light flux amountof light emitted from the light source 52G of the second light emittingoptical system 51G, and a total light flux amount of light emitted fromthe light source 52B of the third light emitting optical system 51B. Forexample, it may be possible to perform switching, so as to emit warmwhite light or to emit blue white light, within the scope of the law.

Moreover, in the seventh embodiment, the first optical element 55 fsynthesizes the first light LD_(R) and the second light LD_(G) bytransmitting the first light LD_(R) first light and reflecting thesecond light LD_(G), and the second optical element 55 s synthesizes thefirst light LD_(R), the second light LD_(G), and the third light LD_(B)by transmitting the first light LD_(R) and the second light LD_(G)synthesized by the first optical element 55 f and reflecting the thirdlight LD_(B). However, for example, it may have a configuration wherethe third light LD_(B) and the second light LD_(G) are synthesized inthe first optical element 55 f, and the third light LD_(B) and thesecond light LD_(G) synthesized by the first optical element 55 f andthe first light LD_(R) are synthesized in the second optical element 55s. In this case, the positions of the first light emitting opticalsystem 51R and the third light emitting optical system 51B of theseventh embodiment are switched. Moreover, in this case, it will have aconfiguration where the third 0th-order light LC_(B) and the second0th-order light LC_(G) are synthesized in the first optical element 55f, and the third 0th-order light LC_(B) and the second 0th-order lightLC_(G) synthesized by the first optical element 55 f and the first0th-order light LC_(R) are synthesized in the second optical element 55s. In the seventh embodiment, a band pass filter that transmits light ofa predetermined wavelength band and reflects light of other wavelengthbands may be used in the first optical element 55 f or the secondoptical element 55 s. The synthesis optical system 55 may combine andsynthesize external shapes of lights emitted from the respective lightemitting optical systems, and is not limited to the above embodiment.

Moreover, in the seventh and eighth embodiments, high order diffractedlight diffracted by the diffraction gratings 54R, 54G, and 54B andemitted from the diffraction gratings 54R, 54G, and 54B is unirradiatedon the projection area PAR, and a light intensity of high orderdiffracted light is set as zero in this projection area PAR. However, alight intensity of high order diffracted light irradiated on theprojection area PAR may be greater than zero, as long as a lightintensity of high order diffracted light irradiated on the projectionarea PAR is smaller than a light intensity of light irradiated on anoutside peripheral edge of the projection area PAR.

Moreover, in the seventh embodiment, the 0th-order lights LC_(R),LC_(G), and LC_(B) advancing and passing through the respectivediffraction gratings 54R, 54G, and 54B may not be synthesized by thesynthesis optical system 55, and may be irradiated on different areas ofthe projection area PAR. However, as described above, in order to reducea driver or the like from being unnecessarily aware of the projectionarea PAR, it is preferable that the 0th-order lights LC_(R), LC_(G), andLC_(B) advancing and passing through the respective diffraction gratings54R, 54G, 54B are synthesized.

Moreover, in the seventh and eighth embodiments, while the projectionarea PAR overlaps with a part of the first area LA1, it may be includedwithin the first area LA1. Moreover, while the projection area PAR doesnot include a position having the highest light intensity L_(H) withinthe light intensity distribution of high order diffracted light, it mayinclude this position. In this case, the brightest area within the lightdistribution pattern PTN_(L) of the low beam L will be mostly unchanged,regardless of whether or not the light intensity of the 0th-order lightis large. Accordingly, the light intensity distribution of the lightdistribution pattern PTN_(L) of the low beam L can be more smoothlyformed, on the basis of a position having a highest light intensitywithin the light intensity distribution of high order diffracted light.

In the seventh and eighth embodiments, the light intensity of theprojection area PAR is lower than the highest light intensity L_(H)within the light intensity distribution of high order diffracted light.However, the light intensity of the projection area PAR may be equal toor more than the highest light intensity L_(H) within the lightintensity distribution of high order diffracted light. In this case, itis preferable that the projection area PAR is included within the firstarea LA1, and it is more preferable that the projection area PAR isincluded at a position having the highest light intensity L_(H) withinthe light intensity distribution of high order diffracted light.

In the seventh and eighth embodiments, the light distribution patternPTN_(L) of the low beam L is formed as a light distribution pattern fordark place illumination. However, it is not limited to a lightdistribution pattern PTN_(L) of the low beam L, if it is a lightdistribution pattern for dark place illumination. Note that, a lightdistribution pattern for dark place illumination is used at night or indark places such as tunnels. For example, there are cases where a lightdistribution pattern of the low beam L, and a light distribution patternof light for visually recognizing a sign positioned outside, forexample, above this light distribution pattern, are formed as a lightdistribution pattern for dark place illumination. In this case, it ispreferable that light for visually recognizing a sign is included inhigh order diffracted light diffracted by the respective diffractiongratings 54R, 54G, and 54B. Moreover, for example, a light distributionpattern of a high beam may be formed as a light distribution pattern fordark place illumination.

Moreover, in the seventh and eighth embodiments, a headlight of anautomobile is exemplified as the vehicle headlight 1. However, theseventh and eighth embodiments are not limited to a headlight of anautomobile, and may be a headlight of another vehicle. Further, theseventh and eighth embodiments are not limited to a headlight, and maybe a lamp such as a rear light, a tail light, a brake light, or anindicator light.

That is, the present invention exemplified in the seventh and eighthembodiments may be a vehicle illumination lamp such as follows. Namely,the vehicle illumination lamp includes a light source, and a diffractiongrating that diffracts light incident from the light source. Lightemitted from the diffraction grating is irradiated in a lightdistribution pattern having a predetermined light intensitydistribution. Also, in the projection area of light advancing andpassing through the diffraction grating among the light distributionpattern, a light intensity of light diffracted by the diffractiongrating and irradiated on the projection area is smaller than a lightintensity of light irradiated on an outside peripheral edge of theprojection area. It can be easily operated, if such a vehicleillumination lamp.

Ninth Embodiment

Next, a ninth embodiment of the present invention will be described.Note that, overlapping descriptions attached with the same referencenumerals, except for particular descriptions, will be omitted forconstituent elements the same or equivalent to those of the firstembodiment. FIG. 17 is a cross-sectional view schematically showing avehicle that includes a vehicle headlight according to the presentembodiment. FIG. 18 is an enlarged view of an optical system unit 50 ofa vehicle headlight 1 shown in FIG. 17 . As shown in FIGS. 17 and 18 ,while the configuration of the vehicle headlight 1 in the presentembodiment is the same as the configuration of the vehicle headlight 1in the first embodiment, a light distribution pattern of light emittedby the vehicle headlight 1 of the present embodiment is different to alight distribution pattern of light emitted by the vehicle headlight 1of the first embodiment.

The diffraction grating 54R of the present embodiment diffracts laserlight emitted from the collimator lens 53R so as to have a predeterminedlight distribution pattern. Specifically, the diffraction grating 54R,in the synthesis optical system 55 described later, diffracts laserlight incident from the collimator lens 53R so that lights respectivelyemitted from the first light emitting optical system 51R, the secondlight emitting optical system 51G, and the third light emitting opticalsystem 51B have a light distribution pattern of a low beam. A lightintensity distribution is also included in this light distributionpattern. Accordingly, the diffraction grating 54R of the presentembodiment diffracts laser light incident from the collimator lens 53R,so as to have a light intensity distribution based on a light intensitydistribution of a light distribution pattern of the low beam L, alongwith laser light emitted from the diffraction grating 54R having a sameexternal shape as an external shape of a light distribution pattern ofthe low beam L. In this way, a red component of light of a lightdistribution pattern of the low beam L is emitted from the first lightemitting optical system 51R. In the present embodiment, a red componentof light emitted from the first light emitting optical system 51R is setas first light L_(R).

The diffraction grating 54G diffracts laser light emitted from thecollimator lens 53G so as to have a predetermined light distributionpattern, and the diffraction grating 54B diffracts laser light emittedfrom the collimator lens 53B so as to have a predetermined lightdistribution pattern. Specifically, the diffraction gratings 54G and54B, in the synthesis optical system 55, respectively diffract laserlight incident from the collimator lenses 53G and 53B so that lightsrespectively emitted from the first light emitting optical system 51R,the second light emitting optical system 51G, and the third lightemitting optical system 51B have a light distribution pattern of the lowbeam L. A light intensity distribution is also included in the lightdistribution pattern, such as described above. Accordingly, thediffraction gratings 54G and 54B of the present embodiment respectivelydiffract laser light incident from the collimator lenses 53G and 53B, soas to have a light intensity distribution based on a light intensitydistribution of a light distribution pattern of the low beam L, alongwith laser light respectively emitted from the diffraction gratings 54Gand 54B having a same external shape as an external shape of a lightdistribution pattern of the low beam L. In this way, a green componentof light of a light distribution pattern of the low beam L is emittedfrom the second light emitting optical system 51G, and a blue componentof light of a light distribution pattern of the low beam L is emittedfrom the third light emitting optical system 51B. In the presentembodiment, a green component of light emitted from the second lightemitting optical system 51G is set as second light L_(G), and a bluecomponent of light emitted from the third light emitting optical system51B is set as third light L_(B). Therefore, in the present embodiment,the first light L_(R) has a longest wavelength, and the wavelengthbecomes shorter in the order of the second light L_(G) and the thirdlight L_(B).

The synthesis optical system 55 includes a first optical element 55 fand a second optical element 55 s. The first optical element 55 f is anoptical element that synthesizes the first light L_(R) emitted from thefirst light emitting optical system 51R and the second light L_(G)emitted from the second light emitting optical system 51G. In thepresent embodiment, the first optical element 55 f synthesizes the firstlight L_(R) and the second light L_(G) by transmitting the first lightL_(R) and reflecting the second light L_(G). Moreover, the secondoptical element 55 s is an optical element that synthesizes the firstlight L_(R) and the second light L_(G) synthesized by the first opticalelement 55 f and the third light L_(B) emitted from the third lightemitting optical system 51B. In the present embodiment, the secondoptical element 55 s synthesizes the first light L_(R), the second lightL_(G), and the third light L_(B) by transmitting the first light L_(R)and the second light L_(G) synthesized by the first optical element 55 fand reflecting the third light L_(B). An optical filter, in which anoxide film is layered on a glass substrate, can be included as such afirst optical element 55 f and second optical element 55 s. Bycontrolling the type and thickness of this oxide film, it is possible toform a configuration that transmits light having a wavelength longerthan a predetermined wavelength, and reflects light having a wavelengthshorter than this wavelength.

In this way, light in which the first light L_(R), the second lightL_(G), and the third light L_(B) are synthesized is emitted from thesynthesis optical system 55.

Next, the emission of light by the vehicle headlight 1 of the presentembodiment will be described.

First, by supplying power from a power source that is not illustrated,laser light is emitted from the respective light sources 52R, 52G, and52B. As described above, red laser light is emitted from the lightsource 52R, green laser light is emitted from the light source 52G, andblue laser light is emitted from the light source 52B. The respectivelaser lights are collimated by collimator lenses 53R, 53G, and 53B, andafterwards are incident on the diffraction gratings 54R, 54G, and 54B.Then, as described above, the respective laser lights are diffracted bythe diffraction gratings 54R, 54G, and 54B, the first light L_(R) thatis a red component of light of a light distribution pattern of the lowbeam L is emitted from the first light emitting optical system 51R, thesecond light L_(G) that is a green component of light of a lightdistribution pattern of the low beam L is emitted from the second lightemitting optical system 51G, and the third light L_(B) that is a bluecomponent of light of a light distribution pattern of the low beam L isemitted from the third light emitting optical system 51B.

In the synthesis optical system 55, first, the first light L_(R) and thesecond light L_(G) are synthesized and emitted by the first opticalelement 55 f. The first light L_(R) and the second light L_(G)synthesized by the first optical element 55 f are synthesized with thethird light L_(B) by the second optical element 55 s. At this time,since the respective lights have an external shape the same as theexternal shape of the low beam L, the external shapes of the respectivelights will be synthesized by matching each other. Namely, the positionsof each of the light emitting optical systems and the synthesis opticalsystem are finely adjusted, so that the external shape of the firstlight L_(R), the external shape of the second light L_(G), and theexternal shape of the third light L_(B) are combined by the synthesisoptical system such as described above. In this way, light in which thered first light L_(R), the green second light L_(G), and the blue thirdlight L_(B) are synthesized becomes white light. Moreover, since thefirst light L_(R), the second light L_(G), and the third light L_(B) arelight intensity distributions based on a light intensity distribution ofa light distribution pattern of the low beam L such as described above,white light in which these lights are synthesized will become a lightintensity distribution of the low beam L.

In this way, synthesized white light is emitted from the opening 59H ofthe cover 59, and this light is emitted from the vehicle headlight 1 viathe front cover 12. Since this light has a light distribution pattern ofthe low beam L, the irradiated light becomes the low beam L.

FIG. 19A and FIG. 19B are diagrams showing a light distribution patternfor night illumination in the present embodiment, specifically, FIG. 19Ais a figure showing a light distribution pattern of a low beam, and FIG.19B is a figure of a light distribution pattern of a high beam. In FIG.19A and FIG. 19B, S shows a horizontal line, and a light distributionpattern is shown by a bold line. Among a light distribution pattern ofthe low beam L that is a light distribution pattern for nightillumination shown in FIG. 19A, an area LA1 is an area having a highestlight intensity, and the light intensity decreases in the order of anarea LA2, and an area LA3. Namely, the respective diffraction gratings54R, 54G, and 54B diffract light so that synthesized light forms a lightdistribution pattern including a light intensity distribution of the lowbeam L. Note that, as shown by a broken line in FIG. 19A and FIG. 19B,light having a light intensity lower than that of the low beam L may beirradiated from the vehicle headlight 1 to above a position where thelow beam L is irradiated. This light is used as light OHS for visuallyrecognizing a sign. In this case, it is preferable that this light OHSfor visually recognizing a sign is included in the diffracted lightemitted from the respective diffraction gratings 54R, 54G, and 54B.Moreover, in this case, it can be understood that a light distributionpattern for night illumination is formed by the low beam L and the lightOHS for visually recognizing a sign. Note that, a light distributionpattern for night illumination is not only used at night, but is alsoused in a dark place such as a tunnel.

Incidentally, white reference light from the light source is incident onthe hologram element of the vehicle headlight of Patent Document 1, anda light distribution pattern of a low beam is formed by this diffractedlight. However, white light is light obtained by synthesizing light of aplurality of wavelengths. Incidentally, a hologram element, which is onetype of diffraction grating, has a wavelength dependency. Therefore,light of mutually different wavelengths included in white tends to havemutually different light distribution patterns depending on the hologramelement. Accordingly, in the case where a low beam is irradiated by thevehicle headlight described in Patent Document 1, light bleeding fromwhich lights of different colors emerges will occur near edges of alight distribution pattern of the low beam. Accordingly, there is ademand to suppress color bleeding while reducing the size.

Accordingly, the vehicle headlight 1 of the present embodiment includesthree of a first light emitting optical system 51R, a second lightemitting optical system 51G, and a third light emitting optical system51B having light sources 52R, 52G, and 52B and diffraction gratings 54R,54G, and 54B, and a synthesis optical system 55 that synthesizes lightemitted from the respective light emitting optical systems. The lightsources 52R, 52G, and 52B in the respective light emitting opticalsystems emit light of mutually different predetermined wavelengths, andthe diffraction gratings 54R, 54G, and 54B in the respective lightemitting optical systems diffract light from each of the light sources52R, 52G, and 52B so that light synthesized by the synthesis opticalsystem 55 has a light distribution pattern of the low beam L.

Therefore, since the vehicle headlight 1 of the present embodiment canform a light distribution pattern of the low beam L without using ashade, it is possible to reduce in size compared to a vehicle headlightusing a shade. Moreover, in the respective light emitting opticalsystems, light of a predetermined wavelength emitted from the lightsources 52R, 52G, and 52B is separately diffracted by the diffractiongratings 54R, 54G, and 54B, and a light distribution pattern is formed.At this time, in the respective light emitting optical systems, sincelight diffracted by the diffraction gratings 54R, 54G, and 54B has apredetermined wavelength such as described above, it is possible tosuppress color bleeding from occurring near edges of a lightdistribution pattern in the lights emitted from the respectivediffraction gratings 54R, 54G, and 54B, even if the diffraction gratings54R, 54G, and 54B have a wavelength dependency. In this way, lighthaving a light distribution pattern in which color bleeding issuppressed is synthesized by the synthesis optical system 55, and thelight distribution pattern of the low beam L is formed. Therefore, thelow beam L irradiated by the vehicle headlight 1 of the presentembodiment can suppress color bleeding from appearing near edges of alight distribution pattern. Moreover, in the present embodiment, sincethere are three light emitting optical systems that emit light ofmutually different wavelengths, light of a desired color can be emitted,by adjusting the light intensity of light emitted from the respectivelight emitting optical systems.

Moreover, the vehicle headlight 1 of the present embodiment has therespective lights emitted from the first light emitting optical system51R, the second light emitting optical system 51G, and the third lightemitting optical system 51B synthesized by the synthesis optical system55, and the synthesized light is emitted from the vehicle headlight 1.Accordingly, it is possible to suppress color bleeding from occurringnear edges of a light distribution pattern irradiated regardless of adistance from the vehicle, more than the case where the respectivelights emitted from the first light emitting optical system 51R, thesecond light emitting optical system 51G, and the third light emittingoptical system 51B are separately emitted from the vehicle headlight 1,and synthesized outside the vehicle headlight 1. Moreover, since lightsemitted from the respective light emitting optical systems aresynthesized by the synthesis optical system 55, and then emitted fromthe vehicle headlight, the emission portion of light of the vehicleheadlight 1 can be made small, and the degree of freedom of the designcan be improved.

Tenth Embodiment

Next, a tenth embodiment of the present invention will be described indetail with reference to FIG. 20 . Note that, overlapping descriptionsattached with the same reference numerals, except for particulardescriptions, will be omitted for constituent elements the same orequivalent to those of the ninth embodiment.

FIG. 20 is a figure showing, similar to FIG. 18 , an optical system unitof a vehicle headlight according to the present embodiment. As shown inFIG. 20 , the optical system unit 50 of the vehicle headlight of thepresent embodiment is different to the optical system unit 50 of theninth embodiment for the point of not including the synthesis opticalsystem 55, and emitting the respective lights emitted from the firstlight emitting optical system 51R, the second light emitting opticalsystem 51G, and the third light emitting optical system 51B from thecover 59, in a state where not synthesized. In the present embodiment,the first light emitting optical system 51R, the second light emittingoptical system 51G, and the third light emitting optical system 51B havean irradiation direction of light on an opening 59H side of the cover59.

In the present embodiment, similar to the ninth embodiment, in thediffraction grating 54R of the first light emitting optical system 51R,the diffraction grating 54G of the second light emitting optical system51G, and the diffraction grating 54B of the third light emitting opticalsystem 51B, respectively, light is diffracted so that synthesized lightforms a light distribution pattern of the low beam L. The first lightL_(R) emitted from the diffraction grating 54R, the second light L_(G)emitted from the diffraction grating 54G, and the third light L_(B)emitted from the diffraction grating 54B are respectively emitted fromthe opening 59H of the cover 59, and irradiated to the outside of thevehicle headlight via the front cover 12. At this time, the first lightL_(R), the second light L_(G), and the third light L_(B) are irradiatedso that the external shapes of the respective light distributionpatterns substantially match each other at a focal position separated apredetermined distance from the vehicle. This focal position is, forexample, a position 25 m away from the vehicle. Namely, in the presentembodiment, the irradiation directions of light of the first lightemitting optical system 51R, the second light emitting optical system51G, and the third light emitting optical system 51B are finelyadjusted, so that the external shapes match each other such as describedabove. Note that, in the present embodiment, as shown by a broken linein FIG. 19A, light OHS for visually recognizing a sign may be emitted.In this case, similar to the ninth embodiment, it is preferable thatthis light OHS for visually recognizing a sign is included in thediffracted light emitted from the respective diffraction gratings 54R,54G, and 54B.

According to the vehicle headlight of the present embodiment, since thesynthesis optical system 55 of the ninth embodiment is not used, it ispossible to form a simple configuration. Note that, the external shapeof the first light L_(R), the external shape of the second light L_(G),and the external shape of the third light L_(B) of the presentembodiment tend to slightly deviate from each other except for at thefocal position. However, when compared with diffracted light obtained byhaving white light incident on one diffraction grating, it is possibleto suppress this deviation of the external shapes. Therefore, accordingto the present embodiment, a vehicle headlight can be realized that iscapable of suppressing color bleeding while being reduced in size.

Note that, in the ninth and tenth embodiments, while the low beam L isemitted from the vehicle headlight 1, the ninth and tenth embodimentsare not limited to this if light for night illumination is emitted. Forexample, a high beam H may be emitted from the vehicle headlight 1. Inthis case, light of a light distribution pattern of the high beam H,which is the light distribution pattern for night illumination shown inFIG. 19B, is irradiated. Note that, among the light distribution patternof the high beam H in FIG. 19B, an area HA1 is an area having a highestlight intensity, and an area HA2 is an area having a light intensitylower than that of the area HA1. Namely, the respective diffractiongratings diffract light so that synthesized light forms a lightdistribution pattern including the light intensity distribution of thehigh beam H.

Moreover, in the ninth and tenth embodiments, the first light emittingoptical system that emits a red component of the first light L_(R), thesecond light emitting optical system that emits a green component of thesecond light L_(G), and the third light emitting optical system thatemits a blue component of the third light L_(B), are included. However,in the vehicle headlight of the ninth and tenth embodiments, at leasttwo light emitting optical systems have light sources that respectivelyemit light of mutually different predetermined wavelengths, and thenumber of light emitting optical systems and the lights emitted from thelight sources will not be limited, as long as the synthesized lightbecomes a light distribution pattern for night illumination. Forexample, in the case where there are two light emitting optical systems,there may be yellow light of night illumination, by having one lightemitting optical system emit green light and the other light emittingoptical system emit red light, or there may be white light of nightillumination, by having one light emitting optical system emit bluelight and the other light emitting optical system emit yellow light.

Moreover, the number of light emitting optical systems may be three ormore. In this case, for example, a fourth light emitting optical systemthat emits a yellow component of light of the low beam L may beprovided. For example, in addition to the red, green, and blue lightemitting optical systems, the fourth light emitting optical system mayemit a yellow component of light of the low beam L. Moreover, in thecase where a light intensity of a part of red, green, and blue is low,the fourth light emitting optical system may emit a color component oflight the same as the color with a low light intensity.

Moreover, in the ninth and tenth embodiments, a white balance adjustmentcircuit may be further provided. This white balance adjustment circuitcan achieve a desired white balance, by controlling a total light fluxamount of light emitted from the light source 52R of the first lightemitting optical system 51R, a total light flux amount of light emittedfrom the light source 52G of the second light emitting optical system51G, and a total light flux amount of light emitted from the lightsource 52B of the third light emitting optical system 51B. For example,it may be possible to perform switching, so as to emit warm white light,or to emit blue white light, within the scope of the law.

Moreover, in the ninth embodiment, the first optical element 55 fsynthesizes the first light L_(R) and the second light L_(G) bytransmitting the first light L_(R) first light and reflecting the secondlight L_(G), and the second optical element 55 s synthesizes the firstlight L_(R), the second light L_(G), and the third light L_(B) bytransmitting the first light L_(R) and the second light L_(G)synthesized by the first optical element 55 f and reflecting the thirdlight L_(B). However, for example, it may have a configuration where thethird light L_(B) and the second light L_(G) are synthesized in thefirst optical element 55 f, and the third light L_(B) and the secondlight L_(G) synthesized by the first optical element 55 f and the firstlight L_(R) are synthesized in the second optical element 55 s. In thiscase, the positions of the first light emitting optical system 51R andthe third light emitting optical system 51B of the ninth embodiment areswitched. Moreover, in the ninth embodiment, a band pass filter thattransmits light of a predetermined wavelength band and reflects light ofother wavelength bands may be used in the first optical element 55 f orthe second optical element 55 s. The synthesis optical system 55 maycombine and synthesize external shapes of lights emitted from therespective light emitting optical systems, and is not limited to theconfiguration of the ninth embodiment or the above configuration.

As described above, according to the present invention, a vehicleillumination lamp that is easy to operate, and a vehicle headlight thatcan suppress color bleeding while being reduced in size are provided,which are capable of being used in a field such as vehicle illuminationlamps of automobiles or the like.

REFERENCE SIGNS LIST

-   1 vehicle headlight-   10 housing-   20 lamp unit-   30 heat sink-   40 cooling fan-   51R first light emitting optical system-   51G second light emitting optical system-   51B third light emitting optical system-   52R, 52G, 52B light source-   54R, 54G, 54B diffraction grating-   55 synthesis optical system-   55 f first optical element-   55 s second optical element

The invention claimed is:
 1. A vehicle illumination lamp, comprising: alight source; and a diffraction grating for diffracting light incidentfrom the light source, wherein light emitted from the diffractiongrating is irradiated in a light distribution pattern having apredetermined light intensity distribution of a vehicle headlamp, and ina projection area of light advancing and passing through the diffractiongrating among the light distribution pattern, a light intensity of lightdiffracted by the diffraction grating and irradiated on the projectionarea is made smaller than a light intensity of light irradiated to anoutside peripheral edge of the projection area.
 2. The vehicleillumination lamp according to claim 1, wherein a total value of thelight intensity of light diffracted by the diffraction grating andirradiated on the projection area and a light intensity of lightadvancing and passing through the diffraction grating and irradiated onthe projection area is made lower than a highest light intensity withina light intensity distribution of light diffracted by the diffractiongrating.
 3. The vehicle illumination lamp according to claim 2, whereinthe light intensity of light diffracted by the diffraction grating andirradiated on the projection area is zero.
 4. The vehicle illuminationlamp according to claim 1, wherein the projection area is includedwithin an area having a light intensity higher than half a value of ahighest light intensity within a light intensity distribution of lightdiffracted by the diffraction grating.
 5. The vehicle illumination lampaccording to claim 4, wherein the projection area includes a positionhaving a highest light intensity within the light intensity distributionof light diffracted by the diffraction grating.
 6. The vehicleillumination lamp according to claim 1, further comprising: a pluralityof light emitting optical systems including one light source and onediffraction grating; and a synthesis optical system for synthesizinglight emitted from the respective light emitting optical systems,wherein the light sources in the respective light emitting opticalsystems emit light of mutually different predetermined wavelengths, andthe diffraction gratings in the respective light emitting opticalsystems emit light from the light sources so that the light synthesizedby the synthesis optical system has the light distribution pattern. 7.The vehicle illumination lamp according to claim 6, wherein lightsadvancing and passing through the diffraction gratings in the respectivelight emitting optical systems are synthesized by the synthesis opticalsystem, and irradiated on the projection area.
 8. The vehicleillumination lamp according to claim 1, further comprising: a pluralityof light emitting optical systems including one light source and onediffraction grating, wherein the light sources in the respective lightemitting optical systems emit light of mutually different predeterminedwavelengths, and the diffraction gratings in the respective lightemitting optical systems emit light from the light sources so as to havethe light distribution pattern at a position separated a predetermineddistance from a vehicle.